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Varsaw, 15th Feb. 1790.

MY DEAR SIR,

I HAD the honor to write you the 1st or the 3th of Feb. I do not recolect, but I gave you the information to apply to the Minister of Svede at Hague, or at Amsterdam for the propositions, (according to what Mr D'Engestrom told me.) They Boths had Orders to Communicate you. I wish with all my heart that could enswer your expectation. I am totaly ignorant what they are, but I would see you to fight against the opresion and Tyranny. Give me the news of every thing. I am, dear Sir, your most humble and most obedient servant, T. KOSCIUSZKO. G. M.

Write me if you please who is Minister from America at Paris; I want to know his name.

This negociation does not seem to have succeeded; and Jones in vain solicited employment from France. Having, therefore, it would appear, spent all the money which he had received for his prizes, he died at Paris in 1792, in great poverty. Colonel Blackden was obliged to raise a subscription to defray the expences of his funeral. The National Assembly voted a deputation of their members to attend upon that occasion.-At a future period we hope to be able to lay be fore our readers an interesting biographical notice of this extraordinary

character.

the new road, however, has displayed an extensive section of the strata; and this circumstance, united with others, has unfolded, in a great measure, the geognostic relations of the beds which form the entire hill.

The distinguished professor of mineralogy in our university makes it a rule to visit this hill, accompanied by the young gentlemen attending his class, and to point out the nature and relations of the rocks. We shall here give, as succinctly as possible, an idea of the succession of these, or of the structure of the hill, such as we gathered from attending the professor

on one of these excursions.

In the course of some building operations at a brewery at the foot of Calton Street, some time ago, (about the beginning of the year 1816) a bed of sandstone, highly siliceous, or of the nature of quartzy sandstone, was exposed to view; and, from the dip and direction of this bed being to the east, it was evident that it passed under the great mass of the hill. Sandstone was also partially displayed in digging the foundation of the large building, in North Back of Canongate, lately erected by Messrs Muir and Wood as a manufactory of musical instruments. Over the sandstone is a bed of porphyry, which, near to the buildings of the Bridewell, extends upwards almost to the level of the new road. To this succeeds a bed of greenstone,

which is visible in the section formed by the new road fronting Bridewell.

ON THE GEOLOGICAL STRUCTURE OF In proceeding upwards, examining the

THE CALTON HILL.

MR EDITOR,

THE new approach to Edinburgh on the south-east, by a road winding over a part of the Calton Hill, and joining Prince's Street at the Register Office, is doubtless one of the most magnificent improvements of which this picturesque capital is susceptible. Our purpose, at present, is, not to enlarge on the beauties and advantages of this new approach, but merely to notice a favour which has, by this improvement, been conferred on mineralogists, certainly without being contemplated by the public-spirited individuals who conceived it. Owing to the uniform covering of debris and of sward on the east side of the Calton Hill, the nature of the rocks constituting a great part of the hill could not be ascertained. The cutting of

series of rocks from the governor's house to the base of Nelson's Monument, we observe a bed of trap-tuff. Over this a bed of porphyry; then a thin bed of greenstone; a second bed of trap-tuff, of no great thickness; another bed of greenstone; a third bed of trap-tuff; and uppermost, a thick mass of porphyry, forming the summit of the hill, and supporting the monument. This bed of porphyry has long been exposed, having many years ago been used as a quarry for affording small stones for laying on the high roads. It is now, however, more inmediately brought into view, in consequence of the fine walk lately made in front of it, by means of the funds collected by the public for affording employment to industrious workmen, thrown idle by the difficulties of the times.

All the beds which have been mentioned dip to the east, so that, in walking eastward, to the first turn of the new road, after passing Bridewell, the beds which pass immediately below Nelson's Monument come to be on a level with the road, and soon after even to dip under it. According ly, we first meet with a bed of greenstone inclining to wacke, and traversed by numerous veins of calcareous spar; and immediately the porphyry of the top comes in view. In proceeding further in the direction towards the east road to Leith, the section on the north side of the new road has displayed a series of thin beds which lie over this porphyry, or which, in geognostic situation, are superior to those which constitute the geographical summit of the hill. They occur in the following order, proceeding from below upwards: Bituminous shale; wacke; sandstone; bituminous shale; wacke; shale with ironstone; wacke; shale and ironstone, (several times repeated); wacke, in a state of decomposition, so as to resemble fullers' earth; bituminous shale and wacke, (several times repeated); and lastly, or geognostically uppermost, a thick bed of sandstone-conglomerate. Quarries have been opened in this bed of sandstone; and the under storey of the new jail was built from it; the upper part of the building having, with good taste, been constructed of finer sandstone.

We thus find that, the Calton Hill consists of many beds of trap rocks, included between two great beds of sandstone; the lower of which is of the kind called quartzy sandstone; and the upper, sandstone-conglome

rate.

The alternation of beds of sandstone and greenstone is seen again at Lochend, to the eastward; and, from the dip and direction of these Lochend beds, we are warranted to conclude that, if projected, they would pass over the Calton Hill. On the other hand, the Castle rock, situated to the westward, consists of beds of sandstone, and a thick bed of basalt; and, on the same data, we conclude, that ⚫ this bed of basalt lies below the great bed of quartzy sandstone, on the ledge of which the High Street of Edinburgh is built, and which was seen in digging the foundation for the Bank of Scotland some years ago, and

more lately in clearing out the foundation for the County Hall of Mid-Lothian; and further, that both pass under the Calton Hill. If all the inclined beds, from the sandstone seen running below the Castle basalt on the west side, to the sandstone and greenstone of Lochend on the east side, be, in the " mind's eye," brought to a horizontal position, so as to exhibit a perpendicular section, the height or thickness becomes indeed surprising.

It may be remarked, that the same individual beds are not, in every part of their extent, of equal thickness; on the contrary, they vary much in this respect. For instance, some one of the several beds of greenstone, which are thin on the S. E. side of the hill, has acquired considerable thickness where it appears in the quarry opened on the N. E. side of the hill. The bed alluded to lies over the sandstone which has there been quarried, and is covered by a thin bed of bituminous shale. This inequality in thickness, at different parts of the same bed, is a fact perfectly familiar to those accustomed to geognostic observation.

PAT. NEILL.

Canonmills, 2d Aug. 1817.

ABSTRACT, WITH OBSERVATIONS, OF THE EVIDENCE TAKEN BEFORE THE COMMITTEE OF THE HOUSE OF COMMONS ON STEAM-BOATS.

MR EDITOR,

IN the last number of the Scots Magazine, I find inserted a valuable document, the report of the Committee of the House of Commons on steam-boats. In a question, however, in which all classes of the community are so deeply interested, the public will not be satisfied without examining for themselves the evidence from which the report was drawn up. I will frankly say, that the perusal suggested to me views of the subject not exactly agreeing with those which have been adopted by the Committee in their report. On this point, however, your readers may be able to judge, when I lay before them the principal statements actually made by those persons who were examined be fore the Committee.

The main points at issue are, whe ther the engines in sicam-boats ought to be what is called high pressure, or whether they ought to be boilers of

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It is needless to enter minutely into the difference between the structure of the high and low pressure engines; the description, indeed, could hardly be made intelligible without plates. It is enough to say, that in the low pressure, called also the condensing engine, the power of the steam can, with no advantage, be raised above six pounds upon the square inch; it may be raised higher; but there is no temptation to raise it, because no increase in the propelling power of the engine would follow. In the high pressure, on the contrary, every increase of force which the steam receives, will produce a corresponding effect in the power of the engine; it will propel the boat or machine with the greater velocity. The conductors of steam-boats have, therefore, a temptation, when "bent on speed," to increase the power of the steam beyond what the strength of the engine can bear, and consequent ly to produce an explosion.

The steam-boat at Norwich had a high pressure engine. Mr John Taylor states, that it was proved to the pressure of 100 on the square inch, but that no more than 40 lbs. was usually applied. Mr Bramah conceives 60 lbs. to have been the usual pressure; but both are of opinion, that, at the time of the accident, it must have been upwards of 100.

The following are the leading statements on the comparative merits, beginning with those in favour of the low pressure:

Mr Bryan Donkin." Is it your opinion, that a boiler could be made of proper materials, with safety valves, and under proper guard and direction, to make high pressure perfectly safe? That would depend upon the quantity of pressure to be used; a safety valve might be carried to three hundred, or to any assignable force. I think that a high pressure engine may be made safe to a certain extent, but where they are left ad libitum, they never can be perfectly safe.

Is it then your opinion, that in high pressure engines carried to that extent you mention, that danger would always operate?-It would not always operate, but it would be extremely liable to accidents.

"In fact, you yourself would not choose to use a high pressure engine, from the difficulty which exists, either more or less?-That is my opinion."

Mr Timothy Bramah, engineer at Pimlico." Do you think that a high pressure engine, under any guard that can be applied to it, is a safe engine to use in a steam-boat?-I do not conceive it is a proper engine, or a safe one."

Mr Henry Maudeslay, engineer, Lambeth. I never considered high pressure engines were applicable to boats, because the purpose of a high pressure engine is to save water, and water cannot be wanted on board a vessel; the difference between the one and the other makes no saving either in the weight or expence, taking it ultimately, particularly when steamboats are properly contrived. As far as my opinion goes as to steam-engines and steam-boats, I would not go from here to Margate in a high pressure boat."

He is afterwards asked, "According to your experience and knowledge, would a low pressure engine be safe in most cases that can occur ?-I never knew a low pressure engine unsafe, but it appears that high pressure engines have been.”

Mr George Dodd, an extensive proprietor of steam-boats on the Thames." Are all the steam-boats that you now have, or that you have had, used with condensing engines? -They are.

"Has any accident happened dur ing the course of their being used?— The boilers of two have been injured by the imprudence of the engine workers; but no accident of any description could or has occurred to the passengers.

"Did you see the Norwich steampacket which exploded?—I have been on board her, and performed a voyage with her; I went down with a view of purchasing it; I went down for that purpose twice.

"What was your reason for not purchasing it ?-Because it was a high pressure engine, and liable to the accident which has since occurred."

Mr Josias Jessop, civil engineer, Adelphi." There can be no doubt that an engine of low pressure must be more secure than one of high pressure; for although they may be both easily made secure originally, yet from

the natural wear and tear, both are liable to accidents. If an accident happen to one of a high pressure, its consequences certainly will be more dangerous than that of a low pressure engine."

The following testimonies go to prove a contrary opinion:

Alexander Tilloch, editor of the Philosophical Magazine.-" My opinion is, that, attending to what should be attended to in every steam-engine, and employing proper engineers, a steam-engine would be perfectly safe, whether with high pressure or low pressure."

Mr Andrew Vivian, miner, Cornwall.-"What accidents have happened to steam boilers within your own knowledge, working either with low or high pressure steam?-I have known of no accident with high pressure steam and cast iron boilers; but I have known an accident happen working with Boulton and Watt's low pressure engine, which was on the 28th of November 1811, in Wheal Abraham mine; a wrought iron boiler working with low pressure steam exploded there, and scalded six men, three of whom died in the course of a week afterwards. The steam from low pressure scalds much worse than the steam from high pressure."

Mr Thomas Lean, engineer for Cornwall miners" You are then well acquainted with steam-engines of every various construction ?-Certain ly I am; I see fifty-seven every month.

"Do you conceive that there is any material difference in the respective safety of those engines?-Some of the engines are certainly safer than others.

"Be so good as to state which, and why?-I conceive there is no danger whatever in the use of high pressure steam-engines; and for this reason, that in general, for an engine that is intended to be worked with high steam, the materials are made stronger in proportion than the materials used for steam of low pressure."

I shall now collect the evidence in regard to the comparative merits of a cast or of a wrought iron boiler.

Mr John Taylor," Have you ever seen an explosion of a cast iron boiler?-No, I have not; I have seen the effects at Wells Street; I was upon the ruins immediately af

ter; the effect seemed to be tremendous; there it knocked down the whole building, which was a sugar-house of five or six stories high, and fragments appeared to be thrown in every direction; the boiler itself was shattered into a great number of pieces.

"If that had been a wrought iron boiler and had burst, it would not have produced the same effect?—I think not.

Mr William Chapman.-" Would you not always recommend a boiler to be made of wrought metal on board steam-boats?-On board steam-boats I would recommend them all to be made either of copper or charcoal iron plates, beat under the hammer and not rolled; the resistance of cylindric boilers will be in the inverse ratio of their diameters."

Mr Philip Taylor." The boilers I have generally employed, are constructed of malleable iron, commonly known by the name of charcoal iron, rivetted together and secured by strong wrought iron belts. From observing the danger arising from the introduction of flat cast iron ends, I have terminated the ends of the boilers by wrought iron ones, nearly hemispherical; this mode of construction, as far as my experience goes, combines more strength and durability than any other."

Mr Henry Maudeslay." What is your opinion as to the comparative safety of cast and wrought metal used in boilers?-I consider that wrought iron is extremely safe, compared to cast iron.

"Then, at all events, it is your opinion, that in steam-boats boilers of wrought metal should be used in preference to cast ?—No doubt about it.

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Do you think there is any material difference between the use of copper and wrought iron ?—No, excepting in the greater degree of corrosion to which iron is liable.'

Mr Alexander Galloway." Under all the circumstances of the case, I should most decidedly recommend a condensing engine, a condensing engine with a wrought iron boiler; because, when cast iron becomes subject to high expansion and contraction, the constant repetition of these effects in a very great degree impairs the strength of the boiler."

Mr John Braithwaite," Would

you not recommend on board steam boats, wrought metal boilers to be used in preference to cast ?-Certainly; I have made some discoveries my self in the boilers I have put up, which makes them perfectly safe."

Mr John Hall." I make boilers in cast iron, and I have proved them by an hydraulic press made for the purpose, and have gone as high as 250 pounds to an inch, and that I considered enough; nothing happened." Mr Alexander Tilloch. I would prefer cast iron, contrary to the opinion of many people, and the reason I would prefer it is the same for which it is preferred in making cannon. It is not possible to get thick plates of wrought iron perfect throughout, and you trust at last to rivets in joining them, but cast iron boilers can be made of any strength you please; instead of having a boiler that will stand sixty, it may be made to stand six hundred, of either wrought or cast iron. Another reason why I would prefer cast iron is, that the sheet iron corrodes much quicker, and destroys by oxydation, so that a boiler may be safe when first set up, and stand its proof, but very soon be come unserviceable, or at least comparatively so."

Mr John Steel." Will you give your opinion as to the comparative merits of wrought and cast iron?I cannot conceive as to the safety of the two, that there is any difference whatever, when the steam is used, as it generally is, for high pressure engines to 40 pounds to the inch. If it was required to make the strongest boiler imaginable, I should consider cast iron preferable, because there you can get to an unlimited strength of resistance; wrought iron you can only have of a certain thickness."

Mr William Brunton." What injury do you think is likely to arise from the bursting of a high pressure boiler, composed of wrought iron ?-I conceive the injury would be more partial, in consequence of the fragments being larger; for I do not suppose that the wrought iron boiler would be divided into so many parts as a cast iron boiler would.

"In a steam-boat, what boiler would you most recommend to be used to insure safety to the persons on board; a wrought iron or a cast iron

boiler?-A wrought iron boiler, properly constructed."

Mr Josias Jessop." I think that if the boiler were made of malleable metal, such as iron and copper, it would be an additional security.

"What is the ground of your preference to malleable or wrought metal?It does not burst by an explosion, as brittle metal does, but tears; it would probably rend at the joints.

"You do not mean then to say, that it would be impossible that a malleable boiler would burst, but that it is improbable that it would?—It would burst, but it would not fly in pieces; the rent would create a natural safety valve."

Mr Arthur Woolf, engineer, Cornwall.-" Are your boilers in general made of wrought or cast iron?-Of cast iron wholly; I approve of the cast iron boilers in preference to any mixture of metals.

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"Do you consider that the cast iron boiler, upon the common construction, is equally safe with wrought iron one?-Not upon the common construction that I have seen; some I should have doubted very much; I have seen some that are rather dangerous; my patent consists of one composed of a number of tubes.

"Suppose a cast iron boiler, and a wrought iron boiler of about the same form and capacity, to be exploded by the force of the internal steam, do you think that the mischief likely to be produced by each of those would be equal; taking any form you please, and exploding both, which would do the most mischief? I do not think the wrought iron boiler would separate into so many pieces as the cast iron boiler.

"Then do you think that the explosion of the wrought iron boiler is attended with as much danger as the cast iron boiler?-In every thing, excepting what depends upon the fragments of the iron itself; I have no hesitation in saying, that cast iron boilers are safer than wrought iron boilers."

Mr Andrew Vivian." Do you conceive that there is any difference in the liability to explode between the boilers constructed of wrought and of cast iron ?-I should conceive that cast iron could be made much stronger than wrought

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