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more abundant and diversified than were elsewhere observed. At Bowman's one of the most considerable mines now worked, they are particularly numerous, pervading the superincumbent strata. The vein is about eighteen feet thick, and wrought in galleries. The coal, which is very compact, is detached by blasts. The inclination of the vein is about one foot in four.

There is less uniformity in the angle of inclination and direction of the coal strata in this neighbourhood, than was observed near the Schuylkill. They approach nearer to the horizontal.

the south bank of the river, a wide vein of coal, which rises above the stream with sufficient inclination to run galleries clear of the water. A large tract on the side of the mountain that ascends gradually to the east from the coal bed, has been cleared at the expense of the company, and a village will shortly arise. Coal beds extend several miles higher up the stream.-In value, and good quality, the Lackawanna anthracite compares advantageously with that of the Lehigh. The coal of this region will be conveyed to New York, a distance of 217 miles, through the medium of a canal now constructFrom the abundance of sulphuret of iron in the slateing under the able superintendence of Judge Wright, contiguous to, and dividing coal veins, the springs pro- by the proprietors of the coal bed. This canal comceeding from the coal beds and the Susquehanna are mences at the Hudson near Kingston, and passes to the strongly impregnated with salts. These mineral waters Delaware, 67 miles, through a valley located between often occur, in both mountain and valley, and indicate the Shawangunk mountain, and the gray wacke ranges, spurs from the Catskill. Except near the Delaware, and on approaching the Hudson, where considerable excavation in limestone and other rocks became necessary, there was little difficulty in constructing the work, as for much of the distance it passes through sandy and gravelly loam. For twenty miles it runs on the side of a mountain north of the valley, and at a considerable elevation. At the summit level the canal extends eighteen miles without a lock. It will probably be completed from the Hudson to the Delaware the present season.

beds of coal.

A canal route has recently been surveyed by State commissioners, and located through the valley of Wyoming, on rising ground west of the Susquehanna. When the work is accomplished it will lessen the charge of forwarding coal to market from this vicinity, and the valley of the Lackawanna. From Wilkesbarre to the Chesapeake, the descent is about 500 feet. By the hazardous and precarious medium of the Susquehanna, coal cannot now be conveyed in arks for less than $3 50 the ton, which, with other charges, makes the expense to the mouth of the river, five dollars the ton. The Philadelphia market may be resorted to through the medium of the Union Canal. A canal to connect the Susquehanna with the Lehigh is practicable. The distance to Philadelphia, by this route from Wilkesbarre, is 162 miles; and the lockage required, 1279 feet.

The coal of the Susquehanna is readily kindled in grates of ordinary construction; and by the experiments recorded in No. 2, Vol. X. of the Journal of Science, it has been ascertained, by the editor, to contain double the quantity of hydrogen gas embraced in the anthracites of the Lehigh and Schuylkill, and in bituminous coal, an important characteristic not before suspected. The valley of Wyoming, and its valuable beds and veins of coal, have been correctly described in No. 1, Vol. IV. of the Journal of Science, by Mr. Z. Cist, an able naturalist, whose recent death is lamented by all acquainted with

his merit.

Beds of dark argillaceous schist, of small extent, are in a few places cut through. Limestone, of a good quality for calcining, occurs at the base and in places on the side of the Shawangunk ridge, adjacent to the canal in approaching the Hudson and Delaware, and will be useful to the part of Pennsylvania situated between the Delaware and Susquehanna, in which there is no limestone. The construction of the canal up the Delaware, on its eastern bank, to the Lackawaxen, a distance of twenty miles, will be arduous and expensive. For several miles it is located on the steep rocky side of a mountain. The passage up the valley of the Lackawaxen will be comparatively easy. Parts of this valley are settled, and contain considerable alluvial land. About one thousand feet of lockage are required from the Hudson to the western termination of the canal. The coal bed is to be connected with the canal by a rail-way of a few miles, passing over a considerable eminence. Lumber and coal will for many years be the principal articles transported down the canal. An extension of canal navigation up the Delaware into the state of New York, which is practicable, would enhance the value of the stock. The rates of tofl demanded for coal, will, if maintained, exclude individuals from participating in the coal trade through the medium of this canal. The canal will communicate with a large tract of good graz ing land in Wayne county, a part of the district called The most considerable body of coal in this region is the beech woods, that extends in Pennsylvania and New situated between twenty and thirty miles from the Sus-York about one hundred miles from north to south, and quehanna, at the ragged islands, in a narrow valley, adjacent to the Lackawanna, and in the bed of that stream, which washes the southern base of the Lackawanna mountain, a lofty, rocky chain, that bounds the partially cleared valley of the Lackawanna to the north-west. This mountain is well clothed with trees of diversified verdure. Considerable good pine, and much heavy timber, principally hemlock, maple, beech and birch, is found near its base, and adjacent to the upper part of

I visited several large coal beds and veins in the valley of the Lackawanna; they run in a north-east course; some were wide, and the coal is of good quality. Coal veins are of frequent occurrence from the confluence of the Lackawanna with the Susquehanna to near the head waters of the former river; they are variously inclined, from nearly horizontal to an angle of forty-five degrees. Vegetable impressions are rarely, if ever, contained in the coal slate of these beds and veins.

the river.

from 10 to 50 miles in breadth. It is heavily timbered, principally with beech, maple, hemlock, and birch, with occasional groves of good pine. The soil, often based on hard pan, is tenacious of manure and moisture, and good for grazing and tillage. Its surface is undulating, but rarely mountainous; and a considerable proportion is sufficiently free from stone for the purposes of agricul ture. Viewed from the eastern brow of an elevated range, situated between the Lackawaxen and Lackawanna, this tract of country had the aspect of an imThis coal bed, supposed to be very extensive, is the mense plain; its dense forest was dressed in the gay property of the Hudson and Delaware Canal and Coal hues of autumn, blended with the perennial verdure of Company, and has been penetrated thirty feet without pine and hemlock. The blue peaks of the Catskill finding the termination of the coal.-From this bed, mountains to the northeast, towering far above the ge which rests in nearly a horizontal position, a considera-neral elevation, presented an irregular profile on the ble quantity of excellent coal has been raised, but from its low situation the excavation was soon filled with water. It has been occasionally cleared by pumps propelled by water. It is supposed there is sufficient descent of ground to free it by draining. The quarrying may perhaps be interrupted by freshets. I observed on

verge of the horizon. To the east, beyond the fireseared, barren, rocky ranges of Pike county, the Shawangunk and Highland ranges were distinguished. Emigrants from New England are busily occupied in cutting out farms in the beech woods. The first clearing is a work of toil; but as there are no sprouts from

roots, less labour is eventually required than to subdue some descriptions of oak land. From the little durability of hemlock, beech and maple, in fencing, it may in time be necessary to substitute the loose gray wacke slate of the surface. Old red sand stone occurs in the gray wacke region, and often supports a good soil. Flocks of sheep may here be advantageously introduced. Through the medium of the canal the farmers of Wayne and other counties can be amply furnished with lime and gypsum, so useful in agriculture.

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aggregate, principally quartz. Its thin lamina are generally in a horizontal position. The lower strata, often in a decomposing state, contain vegetable impressions.This rock usually rests on dark and very fissile argillaceous schist, that contains much sulphuret of iron, and forms the roof and floor of numerous beds of bituminous coal, adjacent to these streams, These beds are from a few inches to five feet in thickness, and occur at various altitudes, from 200 feet above the river to a great depth below. The salt works on the Conemaugh and KiskeThe western part of Pennsylvania is abundantly sup- minitas, situated 4 miles apart, are supplied with water plied with bituminous coal, as the eastern is with anthra- by boring. The richest water is procured by penetratcite. It is found on the rivers Conemaugh, Alleghany, ing from 4 to 500 feet. Copper tubes, 13 inches in diand Monongahela, and in numerous places to the west ameter, are inserted in the perforation, in which the salt of the Alleghany ridge, which is in general its eastern water rises to a level with the river, accompanied by boundary. It occurs on this mountain at a considerable sulphuretted hydrogen gas, often in considerable quanelevation, and elsewhere in nearly a horizontal position, tity. This gas diminished after many outlets had been alternating with gray sand-stone, that is often micaceous made, and the water did not rise so high. In boring, and bordered by argillaceous schist. The veins are ge- fresh water is seldom found one hundred feet from the nerally narrow, rarely over six feet in width. This mi- surface. Veins of coal and slate were penetrated at vaneral is abundant, and of very good quality near Pitts-rious depths, and narrow beds of limestone, lying deep, burg, where it is valuable for their extensive manufac- were passed through. Some of the lower strata were tures. Beds of bituminous coal are reported as occur-represented as very hard, and others soft; this last is ring in Bedford county, in the north-west part of Lu- supposed to be gypsum. Salt springs are generally zerne, and in Bradford county. In this last county, struck by boring, in the ravine at Kiskeminitas; but in nine miles from the Susquehanna, there is an extensive two instances the ground was penetrated 450 and 650 bed of coal, regarded as bituminous. It has been pene- feet, without meeting salt water. trated thirty feet without fathoming the depth of the

strata.

In the process of manufacturing, salt water is pumped, by horse power, into large troughs, where the earthy Bituminous coal is abundant in Tioga county, state of particles, not held in solution, mostly subside. It is soon New York, adjacent to the route of a feeder required for passed into the boiling pan, which is of cast iron, and a canal contemplated, to connect the Susquehanna with shallow. After boiling a considerable time, it is drawn the Seneca lake. The summit level is forty-four feet off into vats, where the oxide of iron, which is abundant, above the river, and upwards of 400 above the lake.- and carthy salts, subside, together with a portion of muIt occurs on the Tioga, and on the Chemung, a branch riate of soda. The clear brine is passed off to a boiler, of that river. When the canal communication is effect-in which the salt, in fine crystals, is precipitated, and ed, the interchange of anthracite and bituminous coal for salt and gypsum, will he highly valuable for Pennsylvania and New York.

Bituminous coal exists on the Loyal Sock and other streams that descend the western side of the extensive peninsula, situated between the north and west branches of the Susquehanna.

The centre and northern part of this section of the State, is elevated, and mostly in a state of nature. It is crossed by barren ranges, interspersed with valleys and well timbered table land, which will in time be occupied for grazing and tillage. The rocks of the eastern part that fell under my observation, are transition, mostly gray wacke slate. In the western part, adjacent to the west branch of the Susquehanna, limestone is the predominant rock.

This stream, for near fifty miles, winds with a moderate current through a rich valley, with wide alluvial borders often occurring. The valley is bounded to the south by the Bald Eagle Mountain, an extensive elevated rocky range.

then removed to drain. No use is made of the sulphate of soda, of which there is considerable in the water. It would, perhaps, be an improvement of the process, if the precipitation of the iron and earthy salts was effected with less boiling, and the salt crystallized in shallow pans, by a heat short of ébullition; the crystals would be larger, and the salt better and less of it lost. Fine salt, made here, does not answer for the packing of provi sions for exportation.

The salt manufactured at Kiskeminitas and Conemaugh, has some years amounted to 300,000 bushels; it is sold from 20 to 25 cents at the works. The expense of manufacturing does not exceed ten cents the bushel, A large portion of the numerous salt works are establish. ed near the river, in the ravines of the Kiskeminitas, and coal for fuel is procured from veins situated above the works, in the side of the hill, and costs but a cent a bushel.

Less salt is now made on the Conemaugh than in former years, as the springs are weak and the price of the article too low to render it profitable. Seven years Springs, holding in solution muriate of soda, are com- since, there was not a building in the ravine of the Kismon in various parts of the bituminous coal region; they keminitas: it now contains a considerable population, are generally weak near the surface, but deep springs and presents, at the base of a precipitous eminence, disclosed by boring, are often strong. One, containing many dwellings and salt works, from which black bituas much salt as the ordinary waters of Salina, has recent-minous smoke rises in clouds over the hills, or draws ly been discovered, by boring, about twenty miles from through the dusky valley. A clear stream, of consiMontrose, bordering on the State of New York. They derable breadth, is seen rapidly winding among the occur in some of the southern counties of that State, ad-mountains.

jacent to Pennsylvania, and on the Loyal Sock and The western canal of Pennsylvania is located in the other streams, auxiliary to the west branch of the Sus-valley of the Conemaugh, and will add much to the proquehanna.

But the most productive saline springs of Pennsylvania, are situated on the banks of the river Conemaugh and Kiskeminitas, about thirty miles east of Pittsburg. These rivers for many miles wind rapidly through rocky romantic ravines, bordered by hills of from three to four hundred feet elevation, that rise with steep acclivities, presenting mural and projecting precipices of gray sandstone, in places jutting over the road and torrent. The sand stone is ordinarily fine, but is sometimes a coarse

ductiveness of these works, and afford great facilities for the conveyance of salt to the Atlantic and Western market. At present, it is transported on wagons to the east, and in boats, by a precarious navigation, down the Conemaugh and Alleghany river, to Pittsburg.

Considerable salt is made near Pittsburg, from a fountain procured by boring 270 feet. The water is strong, and is raised by a small steam engine. There is little sulphate or carbonate of lime in the water. The salt is white, and of a good quality. This fountain is sufficient

In Huntington county, a quarter of the surface is first rate land, and more than two thirds is under partial improvement. In Centre county there is a large body of There are salt springs on the Chenango, in Mercer table land called the barrens, from which the timber has county. Near the Mahony, in Beaver county, a foun- been cut for the use of furnaces. It is uncultivated, and tain of salt water was procured by boring to the depth held in little estimation from its total destitution of springs of 200 feet. It is probable that strong saline water, in and the impossibility of procuring water by sinking wells. much of the western secondary country, may be obtain--The soil is of an excellent texture for wheat or grazed by boring, as it often occurs contiguous to bitumi- ing, and stone rarely occurs on the surface; but the nous coal, and is indicated by salt licks, and by slate con- earth rests on calcareous rocks replete with fissures, intaining sulphur. to which the rain water sinks to a great depth. This uninhabited tract has in some places a width of five miles and extends thirty; it would afford good ranges for sheep, if cleared of underwood.

1828.1

MOB OF 79.

One man,

collected, and marched through the city, threatening to the first troop had reached the scene. Many of them break open the stores, distribute the goods, and punish were arrested, delivered to the civil authority, and comOn the mitted to prison; and as the sword was very freely used, a those who refused to open their warehouses. morning of the fourth of October, placards were posted considerable number was severely wounded. menacing Robert Morris, Blair M'Clenachan, and many and one boy, were killed in the streets; in the house, others: Mr. Wilson was proscribed by the mob, for hav-captain Campbell was killed, and Mr. Mifflin, and Mr. ing exercised his professional duty as a lawyer, in behalf Samuel C. Morris were wounded. The troop patrolled of certain persons who had been prosecuted for treason; the streets the greater part of the night. The citizens and the punishment decreed for his crime, was banish-turned out en masse; and placed a guard at the powder It was some days before ment to the enemy, yet in New York. But this was not magazine, and the arsenal. the real cause which produced so lamentable an instance order was restored; and the troop, from the part they of popular delusion: that was to be found in the superior had taken, found it necessary to keep much together, and hold themselves in readiness to act in support of talents and respectability of the republican party. each other. Major Lennox was particularly marked out for destruction. He retired to his house at Germantown. Anxious to gain the mob followed, and surrounded it during the night, and prepared to force an entrance. time, he pledged his honour, that he would open the door as day-light appeared.-In the mean time, he contrived to despatch an intrepid woman, who lived in his family, to the city for assistance; and a party of the first troop arrived in season to protect their comrade: but he was compelled to return to town for safety, He was, for a number of years, saluted, in the market, by the title of brother butcher," owing in part, to his having been without a coat on the day of the riot: having on a long coat, he was obliged to cast it aside, to prevent being dragged from his horse.

The gentlemen threatened, determined to defend themselves, and with a number of their friends, to the amount of about thirty or forty, took post at the south west corner of Walnut and Third streets, in a house belonging to, and occupied by, Mr. Wilson: it was then a large, old fashioned brick building, with an extensive garden on Third, and on Walnut streets. Among those in the house, were Messrs. Wilson, Morris, Burd, George Clymer, Daniel Clymer, John T. Mifflin, Allen M'Lane, Sharp Delaney, George Campbell, Paul Beck, Thomas Lawrence, Andrew Robinson, John Potts, Samuel C. Morris, Capt. Campbell, and Generals Mifflin, Nichols, and Thompson. They were provided with arms, but their stock of ammunition was very small. While the mob was marching down, General Nichols, and Daniel Clymer proceeded hastily to the arsensl, at Carpenter's Hall, and filled their pockets with cartridges: this constituted their whole supply.

In the mean time, the mob and militia, for no regular troops took part in the riot, assembled on the commons, while a meeting of the principal citizens took place at the coffee-house. A deputation was sent to endeavour to prevail on them to disperse, but without effect. The first troop of city cavalry, being apprised of what was going forward, and anxious for the safety of their fellow citizens, assembled at their stables, a fixed place of rendezvous, and agreed to have their horses saddled, and ready to mount at a moment's warning. Notice was to be given to as many members as could be found; and a part was to assemble in Dock, below Second streets, and join the party at the stables. For a time a deceitful calm prevailed: at the hour of dinner, the members of the troop retired to their respective homes, and the rebels seized the opportunity to march into the city. The armed men amounted to two hundred, and were commanded by Mills, a North Carolina captain: Faulk ner, a ship-joiner; Pickering, a tailor; and one Bonham; they marched down Chesnut to Second street,-down Second to Walnut-and up Walnut, to Mr. Wilson's house, with drums beating, and two pieces of cannon. They immediately commenced firing on the house, which was warmly returned by the garrison. Finding they could make no impression, the mob procured from a blacksmith's shop in the neighbourhood, a crow-bar, and sledge, and proceeded to force the door. At the critical moment when the door yielded to their efforts, the horse made their appearance: had they succeeded in effecting an entrance, every individual in the house would have, doubtless, been murdered.

After the troop had retired, a few of the members, having received intelligence, that the mob were marching into town, hastened to the established rendezvous. Collecting thus by mere accident, their number only amounted to seven;-these were major Lennox, major Nichols, major William Nichols, Thomas Morris, Alexander Nesbitt, Isaac Coxe, and Thomas Leiper. This small body resolved to attempt the rescue of their fellow citizens. On their route, they were joined by two troopers, belonging to colonel Bayler's regiment, quartered at Bristol, and turning rapidly and suddenly round the corner of Chesnut street, they charged the mob. When the cry of "the horse! the horse!" was raised, the rioters, ignorant of their numbers, dispersed in every direction; but not before two other detachments of

The gentlemen who had comprised the garrison, were advised to leave the city, where their lives were endangered. General Mifflin, and about thirty others, accordingly met at Mr. Gray's house, about five miles below Gray's ferry, where a council was called, and it was resolved to return to town, without any appearance of intimidation. But it was deemed expedient, that Mr. Wilson should absent himself for a time: the others continued to walk as usual in public, and attended the funeral of the unfortunate captain Campbell.

Thus ended this disgraceful affair. Had it not been for the spirited, prompt, and energetic conduct of the first troop, the lives of many valuable citizens, and genuine whigs, would have been sacrificed, and an indelible disgrace entailed upon the city of Philadelphia.

EMLEN ON YELLOW FEVER.

Although several years have elapsed since the city was visited by yellow fever, yet we are not to presume that this will always continue to be the case; it is therefore highly proper to adopt every precaution to prevent its origination in the city, or its introduction from abroad. In the last number of the "N. American Medical and Surgical Journal there is an interesting communication from the late Dr. SAMUEL EMLEN, endeavouring to account for the general appearance of the yellow fever at first in the neighbourhood of the river, by the fogs arising from the river itself, and furnishing some advice as to the preventive measures necessary to be taken-we have made such extracts from this communication as appear to possess general interest.

Having been a member of the Board of Health of this city in the year 1819, when the yellow fever made its appearance in several situations along the wharves of the Delaware, in conjunction with the president of the Board it became my duty to inspect the premises of the sick and to make inquiry into the probable source of the disease. Acting at the time as secretary to the Board, and during the quarantine season receiving daily reports by mail from the Lazaretto physician of all vessels detained as well as those permitted to pass to the city, I was already prepared to decide with some confidence as to the probability of the disease having originated from vessels

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which had arrived from a foreign port. I did not indeed hear of any vessel whatever being so suspected, and I am able to say with certainty as respects the first cases of the disease, which occurred in the ferry tavern on the upper side of Market street, and two fatal cases which occurred in the building contiguous on each side, that there was not at the time, nor had been from the commencement of quarantine, any vessel near them from the West Indies or any sickly port; and I had the assurance from the sick and their friends that they had not been on board of any foreign vessel for some months. Not long after the occurrence of these cases, others were reported, some of which were in situations remote from each other, but all near to the Delaware, amounting to fifteen or twenty patients, and in no instance which came to the knowledge of the Board was there any vessel suspected as the source of the disease. The sick on Market street wharf, and all others where it was practicable, were removed from the city, their apartments cleansed, white washed, &c. and then closed till cool weather.-No farther extension of the disease took place.

than could be pointed out in many other parts of the city and districts where no disease was produced. Besides numerous filthy houses, yards and alleys, in very thickly settled parts of the town, there was every description of accumulated filth scraped from the streets and deposited immediately in the vicinity of tenements occupied by a poor and negligent population in the skirts of the city; as well as large collections of oyster shells in a very offensive condition, and other nuisances, which were frequently complained of to the Board of Health, and by them inspected, but never producing yellow fever.

It must be obvious that miasma varies according to the quality, variety or quantity of the putrescent materials producing it (as the fevers induced by it vary from the simple intermittent to those of the highest malignancy), or that the same effluvia which in the country, from the presence of a purer air, only produces the milder forms of intermitting and remitting fevers, will in a city, where the vitiated air of a crowded population is superadded, produce a malignant fever. But it seems that those putrescent substances which develope a poisonous miasma do not produce a malignant or yellow fever in our cities except on the water's edge. The miasma here must be then either more virulent than that escaping from putrid substances in other parts of the city, or there must be something present on the wharves which is necessary to co-operate in the production of this form of fever, which does not exist in situations farther removed from this locality.

With respect to the local causes said to have existed, some erroneous statements have gone abroad. It was stated in one of our medical journals, that the owner of the ferry on Market street had been accumulating for months a compost heap before his door of vegetable and animal matter for the purpose of manuring his farm in New Jersey. The occupant however had no yard to his house, and it must be well known that no such collection of manure would have been permitted to lie on the wharf before his door. It is true there was some vegetable matter somewhat offensive in an apartment under the tavern occupied by the market people as a deposit for their produce, and the grocery store and small yard adjoining were in a filthy state, but by no means as much so as many other places in the city which had been represented to the Board as nuisances, and where no disease was produced. In several other situations, where the disease appeared, no local filth was dis-into the higher regions of the atmosphere, without procovered.

I was prepared to admit that the preponderance of medical opinion was on the side of the domestic origin of this form of fever, amongst those who had been thoroughly conversant with it from actual observation; though it must be admitted that amongst those on the other side were many equally experienced of the most respectable and distinguished members of the profession. Having had the cases of yellow fever related to occur under my personal observation, and being satisfied that the disease was not in any of the cases referred to brought from abroad, I have presented this statement to the college as additional confirmation of the disease occurring without the slightest foundation for tracing its origin to a foreign source.

Being satisfied on this head, my attention was particularly directed to a consideration of the causes which were likely to operate in producing yellow fever on the wharf, where there appeared to be less of the materials likely to produce a poisonous miasma than were to be found at the same time in many other parts of our city where no fever of the kind ever originated. That this formidable disease has primarily appeared in this situation in all places where its existence has been recorded is, I believe, without any well attested exceptions; and this striking fact is alleged by a very respectable writer, Sir Gilbert Blane, to be a sufficient evidence of itself that The advocates of the the disease is an imported one. local and domestic origin of yellow fever have not advanced reasons in explanation of this circumstance which can be considered satisfactory. It seemed evident that certain agents, not well understood or accurately defined, were necessary to produce this disease on the water's edge, which were not present in other situations in the city remote from this locality. It did not appear that more materials were to be found on the wharves likely to produce mischievous and fatal effluvia

It occurred to me that the most probable cause which gave efficiency to the poisonous effluvia escaping on the wharves in the production of yellow fever was the river itself. That the water evaporating and furnishing a recipient for the poison, it was concentrated in the dense fogs which are seen hovering over its surface and along its borders as soon as the nights begin to lengthen and the autumnal season approaches. It seemed that the miasma which was produced during the heat of the day escaped, by ascending with the imperceptible vapour

ducing any mischievous effects; but as soon as the cool nights and condensation of the watery vapour commenced, it became entangled in the fog, and produced disease by being thus kept in a more concentrated and virulent state within the sphere of respiration. Connected with these phenomena a number of facts presented, which I thought gave additional confirmation to the theory.

The first appearance of fever was found to correspond with the approach of cool nights after previous intense heat had existed for some months; and it appeared to me that if the solar heat, acting upon the sources of the poisonous effluvia on the wharves, was alone sufficient to generate this form of fever without the adventitious help alluded to, as that is often more intense for a long time previous to the commencement of the cool nights and the accompanying fogs or mists than afterwards, we ought to look for its appearance earlier in the season.Besides, as there is certainly more heat during the day at the period of the year when this fever occurs, and consequently more of the effluvia of putrefaction escaping, than during the night, the day-time is the period when the danger of exposure on the wharves would be increased, whereas the danger is unquestionably much greater, if not altogether, at night and early in the morning before the condensed moisture hovering over the river and its margin is dissipated.

It was from the observation of this law in relation to the common autumnal fevers, the co-existence of these with the appearance of fogs along the rivers, over swamps, ponds, mill dams, &c. the materials for producing miasmata being also present, and the evident controlling influence which the motion of the foggy strata seemed to have in the propagation of these fevers, that I was led from analogy to apply a like explanation to the appearance of the yellow fever in the neighbourhood of the wharves. In both instances the disease commences