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Varsaw, 15th Feb. 1790. the new road, however, has displayed MY DEAR SIR,

an extensive section of the strata ; and I had the honor to write you

this circumstance, united with others, the 1st or the 3th of Feb. I do not has unfolded, in a great measure, the recolect, but I gave you the infor- geognostic relations of the beds which mation to apply to the Minister of form the entire hill. Svede at Hague, or at Amsterdam for The distinguished professor of mithe propositions, according to what Mr neralogy in our university makes it a D’Engestrom told me.) They Boths rule to visit this hill, accompanied by had Orders to Communicate you. I the young gentlemen attending his wish with all my heart that could en- class, and to point out the nature and swer your expectation. I am totaly ig- relations of the rocks. We shall here norant what they are, but I would see give, as succinctly as possible, an idea you to fight against the opresion and of the succession of these, or of the Tyranny. Give me the news of every structure of the hill, such as we gathing: Í am, dear Sir, your most thered from attending the professor humble and most obedient servant,

on one of these excursions. T. Kosciuszko. G. M.

In the course of some building opeWrite me if you please who is Mi- rations at a brewery at the foot of nister from America at Paris ; I want Calton Street, some time ago, (about to know his name.

the beginning of the year 1816) a bed

of sandstone, highly síliceous, or of the This negociation does not seem to nature of quartzy sandstone, was ex, have succeeded ; and Jones in vain soli- posed to view; and, from the dip and cited employment from France. Hav- direction of this bed being to the east,

rifore, it would appear, spent it was evident that it passed under the all the money which he had received great mass of the hill. Sandstone was for his prizes, he died at Paris in also partially displayed in digging the 1792, in great poverty. Colonel Black- foundation of the large building, in den was obliged to raise a subscrip- North Back of Canongate, lately erecttion to detray the expences of his fu- ed by Messrs Muir and Wood as a neral. The National Asseinbly voted manufactory of musical instruments. a deputation of their members to at. Over the sandstone is a bed of portend upon that occasion. - At a future phyry, which, near to the buildings of period we hope to be able to lay be the Bridewelí, extends upwards ał. fore our readers an interesting biogra- most to the level of the new road. To phical notice of this extraordinary this succeeds a bed of greenstone, character.

which is visible in the section formed

by the new road fronting Bridewell. ON THE GEOLOGICAL STRUCTURE OF In proceeding upwards, examining the

series of rocks from the governor's MR EDITOR,

house to the base of Nelson's MonuThe new approach to Edinburgh ment, we observe a bed of trap-tuff. on the south-east, by a road winding Over this a bed of porphyry; then a over a part of the Calton Hill, and thin bed of greenstone ; a second bed of joining Prince's Street at the Kegis- trap-tuff, of no great thickness; anoter Office, is doubtless one of the most ther bed of greenstone ; a third bed of magnificent improvements of which trap-tuff ; and uppermost, a thick mass this picturesque capital is susceptible. of porphyry, forming the summit of

Our purpose, at present, is, not to the hill, and supporting the monuenlarge on the beauties and advan- ment. This bed of porphyry has long tages of this new approach, but mere- been exposed, having many years ago ly to notice a favour which has, by been used as a quarry for affording this improvement, been conferred on small stones for laying on the high mineralogists, certainly without being roads. It is now, however, more imcontemplated by the public-spirited mediately brought into view, in conseindividuals who conceived it. Owing quence of the fine walk lately made to the uniform covering of debris and in front of it, by means of the funds of sward on the east side of the Cal- collected by the public for affording ton Hill, the nature of the rocks con- employment to industrious workinen, stituting a great part of the hill could thrown idle by the difficulties of the not be ascertained. The cutting of times.


All the beds which have been men- more lately in clearing out the foun, tioned dip to the east, so that, in dation for the County Hall of Mid-Lowalking eastward, to the first turn of thian ; and further, that both pass the new road, after passing Bridewell, under the Calton Hill

. If all the inthe beds which pass immediately be- clined beds, from the sandstone seen low Nelson's Monument come to be running below the Castle basalt on the on a level with the road, and soon af- west side, to the sandstone and

greenter even to dip under it. According- stone of Lochend on the east side, be, ly, we first meet with a bed of green- in the “mind's eye,” brought to a hostone inclining to wacke, and travers- rizontal position, so as to exhibit a ed by numerous veins of calcareous perpendicular section, the height or spar; and immediately the porphyry thickness becomes indeed surprising. of the top comes in view. In pro- It may be remarked, that the same ceeding further in the direction to- individual beds are not, in every part wards the east road to Leith, the sec- of their extent, of equal thickness ; on tion on the north side of the new road the contrary, they vary much in this has displayed a series of thin beds respect. For instance, some one of which lie over this porphyry, or which, the several beds of greenstone, which in geognostic situation, are superior to are thin on the S. E. side of the hill, those which constitute the geographic has acquired considerable thickness eal summit of the hill. They occur where it appears in the quarry opened in the following order, proceeding on the N. E. side of the hill. The from below upwards : Bituminous bed alluded to lies over the sandstone shale ; wacke ; sandstone; bitumin- which has there been quarried, and is ous shale; wacke; shale with iron- covered by a thin bed of bituminous stone ; wacke; shale and ironstone, shale. This inequality in thickness, (several times repeated); wacke, in a at different parts of the same bed, is a state of decomposition, so as to resem- fact perfectly familiar to those accus, ble fullers' earth; bituminous shale tomed to geognostic observation. and wacke, (several times repeated);

PAT. NEILL, and lastly, or geognostically upper- Canonmills, 2d Aug. 1817. most, a thick bed of sandstone-conglomerate. Quarries have been opened in this bed of sandstone ; and the un

ABSTRACT, WITH OBSERVATIONS, OF der storey of the new jail was built from it; the upper part of the building having, with good taste, been constructed of finer sandstone.

MR EDITOR, We thus find that the Calton Hill In the last number of the Scots consists of many beds of trap rocks, Magazine, I find inserted a valuable included between two great beds of document, the report of the Commitsandstone; the lower of which is of tee of the House of Commons on the kind called quartzy sandstone ; steam-boats. In a question, however, and the upper, sandstone-conglome- in which all classes of the community rate.

are so deeply interested, the public The alternation of beds of sand- will not be satisfied without examinstone and greenstone is seen again at ing for themselves the evidence from Lochend, to the eastward ; and, from which the report was drawn up. I the dip and direction of these Lochend will frankly say, that the perusal beds, we are warranted to conclude suggested to me views of the subject that, if projected, they would pass not exactly agreeing with those which over the Calton Hill. On the other have been adopted by the Committee hand, the Castle rock, situated to the in their report. On this point, howwestward, consists of beds of sand- ever, your readers may be able to stone, and a thick bed of basalt; and, judge, when I lay before them the on the same data, we conclude, that principal statements actually made by this bed of basalt lies below the great those persons who were examined be. bed of quartzy sandstone, on the ledge fore the Committee. of which the High Street of Edin- The main points at issue are, wheburgh is built, and which was seen ther the engines in sican-boais ought in digging the foundation for the to be what is called high pressure, or Bank of Scotland some years ago, and whether they ought to be boilers of


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low pressure ; and whether they ought “ In fact, you yourself would not to be made of cast iron or wrought choose to use a high pressure engine, iron.

from the difficulty which exists, either It is needless to enter minutely in- more or less ?-That is my opinion.” to the difference between the struc- Mr Timothy Bramah, engineer at ture of the high and low pressure en- Pimlico.-" Do you think that a high gines; the description, indeed, could pressure engine, under any guard that hardly be made intelligible without can be applied to it, is a safe engine plates. It is enough to say, that in to use in a steam-boat? I do not the low pressure, called also the con- conceive it is a proper engine, or a densing engine, the power of the safe one.” steam can, with no advantage, be Mr Henry Maudeslay, engineer, raised above six pounds upon the Lambeth.—" I never considered high square inch; it may be raised higher; pressure engines were applicable to but there is no temptation to raise boats, because the purpose of a high it, because no increase in the pro- pressure engine is to save water, and pelling power of the engine would water cannot be wanted on board a vesfollow. In the high pressure, on the sel; the difference between the one contrary, every increase of force which and the other makes no saving either the steam receives, will produce a cor- in the weight or expence, taking it responding effect in the power of the ultimately, particularly when steam: engine ; it will propel the boat or ma- boats are properly contrived. As far chine with the greater velocity. The as my opinion goes as to steam-enconductors of steam-boats have, there- gines and steam-boats, I would not fore, a temptation, when “ bent on go from here to Margate in a high speed,” to increase the power of the pressure boat.” steam beyond what the strength of He is afterwards asked, “ Accordthe engine can bear, and consequent- ing to your experience and knowledge, ly to produce an explosion.

would a low pressure engine be safe The steam-boat at Norwich had in most cases that can occur?-I never a high pressure engine. Mr John knew a low pressure engine unsafe, Taylor states, that it was proved but it appears that high pressure ento the pressure of 100 on the square gines have been." inch, but that no more than 40 lbs. Mr. George Dodd, an extensive was usually applied. Mr Bramah proprietor of steam-boats on the conceives 60 lbs. to have been the Thames.--" Are all the steam-boats usual pressure ; but both are of opi- that you now have, or that you have nion, that, at the time of the accident, had, used with condensing engines ? it must have been upwards of 100. - They are.

The following are the leading state- Has any accident happened durments on the comparative merits, being the course of their being used ?ginning with those in favour of the The boilers of two have been injured low pressure :

by the imprudence of the engine Mr Bryan Donkin.--" Is it your workers; but no accident of any deopinion, that a boiler could be made scription could or has occurred to the of proper materials, with safety valves, passengers. and under proper guard and direc- “ Did you see the Norwich steamtion, to make high pressure perfectly packet which exploded ?-I have been safe? - That would depend upon the on board her, and performed a voyage quantity of pressure to be used; a with her ; I went down with a view safety valve might be carried to three of purchasing it; I went down for hundred, or to any assignable force. that purpose twice. I think that a high pressure engine “ What was your reason for not may be made safe to a certain extent, purchasing it ?--Because it was a high but where they are left ad libitum, pressure engine, and liable to the acthey never can be perfectly safe. cident which has since occurred."

" Is it then your opinion, that in Mr Josias Jessop, civil engineer, high pressure engines carried to that Adelphi.-" There can be no doubt extent you mention, that danger that an engine of low pressure must would always operate ?-It would not be more secure than one of high presą always operate, but it would be ex sure ; for although they may be both tremely liable to accidents.

easily made secure originally, yet from

a su

the natural wear and tear, both are ter; the effect seemed to be tremenliable to accidents. If an accident dous; there it knocked down the happen to one of a high pressure, its whole building, which was consequences certainly will be more gar-house of five or six stories high, dangerous than that of a low pressure and fragments appeared to be thrown engine."

in every direction; the boiler itself The following testimonies go to was shattered into a great number of prove a contrary opinion :

pieces. Alerander Tilloch, editor of the “ If that had been a wrought iron Philosophical Magazine.--" My opi- boiler and had burst, it would not nion is, that, attending to what should have produced the same effect ?-I be attended to in every steam-engine, think not. and employing proper engineers, a Mr William Chapman." Would steam-engine would be perfectly safe, you not always recommend a boiler to whether with high pressure or low be made of wrought metal on board pressure.”

steam-boats ?-On board steam-boats Mr Andrew Vivian, miner, Corn- I would recommend them all to be wall.—“What accidents have happen- made either of copper or charcoal iron ed to steam boilers within your own plates, beat under the hammer and not knowledge, working either with low or rolled; the resistance of cylindric boilhigh pressure steam?-I have known ers will be in the inverse ratio of their of no accident with high pressure diameters." steam and cast iron boilers; but I Mr Philip Taylor.-" The boilers have known an accident happen work. I have generally employed, are coning with Boulton and Watt's low pres- structed of malleable iron, commonly sure engine, which was on the 28th known by the name of charcoal iron, of November 1811, in Wheal Abra- rivetted together and secured by strong ham mine; a wrought iron boiler wrought iron belts. From observing working with low pressure steam ex- the danger arising from the introduce ploded there, and scalded six men, tion of flat cast iron ends, I have terthree of whom died in the course of a minated the ends of the boilers by week afterwards. The steam from wrought iron ones, nearly hemisphelow pressure scalds much worse than rical ; this mode of construction the steam from high pressure.” far as my experience goes, combines

Mr Thomas Leun, engineer for more strength and durability than any Cornwall miners – You are then other." well acquainted with steam-engines of Mr Henry Maudeslay.--"What is every various construction ?--Certain- your opinion as to the comparative ly I am ; I see fifty-seven every safety of cast and wrought metal used month.

in boilers ?-I consider that wrought “Do you conceive that there is any iron is extremely safe, compared to material difference in the respective cast iron. safety of those engines ? -Some of “ Then, at all events, it is your lo the engines are certainly safer than pinion, that in steam-boats boilers of

wrought metal should be used in pre“ Be so good as to state which, and ference to cast ?-No doubt about it. why ?-I conceive there is no danger “ Do you think there is any matewhatever in the use of high pressure rial difference between the use of copa steam-engines; and for this reason, per and wrought iron ?-No, excepto that in general, for an engine that is ing in the greater degree of corrosion intended to be worked with high to which iron is liable.” steam, the materials are made strong- Mr Alexander Galloway." Under er in proportion than the materials all the circumstances of the case, I used for steam of low pressure.” should most decidedly recommend a

I shall now collect the evidence in condensing engine, a condensing enregard to the comparative merits of gine with a wrought iron boiler ; a cast or of a wrought iron boiler. because, when cast iron becomes sub

Mr John Taylor." Have you ject to high expansion and contracever seen an explosion of a cast iron tion, the constant repetition of these boiler?-No, have not; I have effects in a very great degree impairs seen the effects at Wells Street ; I the strength of the boiler."

as upon the ruins immediately afa Mr John Braithwaite," Would



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you not recommend on board steam- boiler?--A wrought iron boiler, pro-
boats, wrought metal boilers to be perly constructed.”
used in preference to cast ? Certain- Mr Josias Jessop.--"I think that
ly; I have made some discoveries mye if the boiler were made of malleable
self in the boilers I have put up, metal, such as iron and copper, it
which makes them perfectly safe.". would be an additional security.

Mr John Hall.I make boilers “What is the ground of your prefer-
in cast iron, and I have proved them ence to malleable or wrought metal ?--
by an hydraulic press made for the It does not burst by an explosion, as
purpose, and have gone as high as 250 brittle metal does, but tears; it would
pounds to an inch, and that I con- probably rend at the joints.
sidered enough ; nothing happened.”

“ You do not mean then to say, Mr Alexander Tilloch." I would that it would be impossible that a prefer cast iron, contrary to the opi- malleable boiler would burst, but that nion of many people, and the reason it is improbable that it would ?-It I would prefer it is the same for would burst, but it would not fly in which it is preferred in making can- pieces; the rent would create a natunon. It is not possible to get thick ral safety valve." plates of wrought iron perfect through- Mr Arthur Woolf, engineer, Cornout, and you trust at last to rivets in wall." Are your boilers in general joining them, but cast iron boilers can made of wrought or cast iron?-Of cast be made of any strength you please ; iron wholly; I approve of the cast instead of having a boiler that will iron boilers in preference to any mixstand sixty, it may be made to stand ture of metals. six hundred, of either wrought or Do you consider that the cast cast iron. Another reason why I iron boiler, upon the common conwould prefer cast iron is, that the struction, is equally safe with sheet iron corrodes much quicker, wrought iron one ?-Not upon the and destroys by oxydation, so that á common construction that I have boiler may be safe when first set up, seen; some I should have doubted and stand its proof, but very soon be very much; I have seen some that are come unserviceable, or at least com- rather dangerous ; my patent consists paratively so."

of one composed of a number of tubes. Mr John Steel." Will you give “ Suppose a cast iron boiler, and a your opinion as to the comparative wrought iron boiler of about the same merits of wrought and cast iron ?- form and capacity, to be exploded by I cannot conceive as to the safety of the force of the internal steam, do the two, that there is any difference you think that the mischief likely to whatever, when the steam is used, as be produced by each of those would it generally is, for high pressure en- be equal ; taking any form you please, gines to 40 pounds to the inch. If it and exploding both, which would do was required to make the strongest the most misehief?—I do not think boiler imaginable, I should consider the wrought iron boiler would sepacast iron preferable, because there you rate into so many pieces as the cast can get to an unlimited strength of iron boiler, resistance ; wrought iron you can only Then do you think that the exhave of a certain thickness.”

plosion of the wrought iron boiler is Mr William Brunton." What in- attended with as much danger as the jury do you think is likely to arise cast iron boiler ?-In every thing, exfrom the bursting of a high pressure cepting what depends upon the fragboiler, composed of wrought iron ?--I ments of the iron itself; I have no conceive the injury would be more hesitation in saying, that cast iron partial, in consequence of the frag- boilers are safer than wrought iron ments being larger; for I do not sup- boilers.” pose that the wrought iron boiler Mr Andrew Vivian." Do you would be divided into so many parts conceive that there is any differas a cast iron boiler would.

ence in the liability to explode be“ In a steam-boat, what boiler tween the boilers constructed of would you most recommend to be wrought and of cast iron ?-I used to insure safety to the persons on should conceive that cast iron could board; a wrought iron or a cast iron be made much stronger than wrought

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