2o<i 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[July. 



He objei-ts to ;in aspect due east, "because there the sun only shines 

 (lie means sliines only) when we are a-bed ;" which, however, depends 

 upon the time people choose to rise, whether before ten o'clock in 

 the forenoon, or after. A no better due west as])ect is aduiireil by 

 him, for that we are assured " is intolerable from the excess of sun 

 dazzling the eye during the greater part of the day." Rooms so 

 situated, must of course be habitable only in the depth of winter or in 

 cloudy \\ eather. It seldom happens that the sun is complained of as 

 being an exceedingly unwelcome guest ; but whenever he is so, we 

 can very easily prevent his intrusion into our rot)ms, by means of blinds 

 and muslin curtains, which, if intended for any purpose at all, are in- 

 tended to shut him out. Tlie objection alleged against an aspect full 

 west is deserving of consideration, because it would follow that in 

 front so turned tiie windows ought to be fewer, that is, the piers 

 much wider between them than if the aspect were east or north, a 

 circumstance I believe wholly disregarded by architects, certainly not 

 attended to in street building. 



The very worst as|)ect of all, we are assured, is a south-west, be- 

 cause more exi)osed than any other to driving rains. In corroboration 

 of this we are told of a heavy storm of wind and rain which pelted 

 against the windows at Organ Hall, while from those on the other side 

 of the house, the view appeared perfectly clear. This driving of rain 

 against the windows, Mr. R. considers highly disagreeable ; yet if 

 most otlier persons agree with him in such dislike, my own taste must 

 be singularly ])erverse or capricious, for I know of nothing that con- 

 veys so intense an idea of indoor comfort and security, than the rattling 

 of wind and rain against the glass which defies their attacks. It is 

 one of those enjoyments for w'hich a Sybarite might be allowed to sigh. 



I will not pursue Repton's remarks any further, except to sav tliat 

 after all they amount to very little if any thing, to nothing more than 

 that, of the four aspects of a house having r(joms facing all of them, 

 three will \>c bad, unless the south-east, instead of due soiith, be chosen 

 for one of them, in which case however, one of the aspects must be 

 the very worst, namely, the so much reprobated south-west. I should 

 therefore say that the safest and best rule is, whenever there is any 

 particular prospect afforded by the situation, to be determined chietly 

 by that, and to take care that it shall be connnanded by the principal 

 sitting rooms, let the aspect thus given to them be what it may ; 

 shoukl that not Ije the most advantageous, there would still be other 

 aspects for other rooms, where prospect might be dispensed with. 



C. 



ON BLASTING ROCKS. 



Sir, — Having seen in your Journal of May last two very interesting 

 accounts of blasting rocks by the aid of galvanism, on plans lately in- 

 troducc^d by Colonel Pasley and Mr. Roberts, grounded on the pv'm- 

 ciple of bringing to an intense red heat a fine iron, steel, or platinum 

 wire, as originally proposed by Dr. Hare, of Philadelphia, I am 

 tempted to trouble you with a few remarks on the advantages stated l.iy 

 Mr. Roberts to be derived by lea\ing a column of atmospheric air 

 above and below the charge of powder, as also the increase of power 

 which is ol5tained by doing away with the necessity of a vent hole. 



If then, in accordance with Mr. Robin's experiments, we suppose 

 that the flame of gunpowder has a temperatute not exceeding that of 

 iron heated to its most extreme degree of red heart, it will ex- 

 pand the air which it penetrates, in the ratio to its former bulk of 4 to 

 1, or induce an increase of pressure of nearly GOlbs on the scpuire inch ; 

 this on the hypothesis of this rate of temperature must be a maximum 

 for the coolness of the surface on'which it acts, as also the inferior 

 temperature of the air must reduce that of the flame somewhat below 

 that of the above standard. Mr. Robins likewise determines that his 

 experiments for the force of gunpowder when inclosed on all sides, as 

 exerting a pressure of 14,7501bs. on the square inch. If we suppose 

 that this is expanded in the ratio of 3 to 1, by leaving a volume of air, 

 equal to the cubic content of the powder, above and below the charge, 

 also that the square surface acted on is increased in the same ratio, we 

 will have in accordance with tlie law of the elasticity, being inversely 

 as the volume, a pressure of 4,9171bs. on the square inch, one-third 

 less than if the jiowder had been inclosed on all sides, b\it acting over 

 three times the surface, and hence, as deduced from the statical l.iw 

 of virtual velocities producing the same virtual effect ; to which, then, 

 if we add the increase of ISOlbs., by the expansion of the air, we pro- 

 cure an addition of power of 1-82'nd ])art of that which we had if no 

 air at all had been employod. From this it may be deduced that (he 

 larger the proportion of air, the greater will be the addition of power, 

 but this, I am of opinion, will be in a great degree counterbalanced by 

 the greater extent of cooling surface, and consequent smaller degree of 

 elasticity of the atmospheric column, With regard to the loss of 



])Ower by vent holes, it is obvious that it will be proportional to the 

 ([uantity of fluid which escapes by such a]iertures, and this will be 

 equal to the velocity of the fluid multiplied by the area of the aper- 

 ture. In order to deternnne this velocity, the best method is, perhaps, 

 to find the height of a homogeneous column, of the same fluid capable 

 of producing the same ]iressure as that to which the fluid is subjected, 

 for then the fluid would rush into a vacuum with the velocity a heavy 

 body would acquire by falling through the height of the homogeneous 

 cohnnn. If, however, the fluid rushes into atmospheric air, instead of 

 a \acuum, the velocity will be that which a heavy body will accjuire, by 

 falling through the diiference between the heights of homogeneous 

 columns of the fluids of greatest elastic force equivalent to the pressures. 

 Thus, if as Mr. Robins states, the elasticity of fired gunpowder is 

 ecpial to a pressure of 14,750 on the square inch, and the height of a 

 column of the same fluid capable of ]iroducing this pressure is /i, 

 putting //' equal to the height of a colunni of the same fluid capable of 

 exerting a pressure the same as that of atmosplieric air, viz.. 151bs. 

 nearly on the square inch, the velocity per second,through the vent hole 

 into air will be determined by the formula v ^ 8 ^/ h — h'. These 

 heights may be procured as follows : — Gunpowder has very much the 

 same density as water, and is supposed to occupy a volume of 1,000 

 less than its generated gas, when this latter exerts a pressure of 

 14,7501bs. on tlie square inch. Now, the height of a column of water 

 at GO" temperature, capable of producing a pressure of lib. on the 

 square inch, is'2-31 feet, but the gas of gunpowder having one thousand 

 times the volume of its generating matter, and consequently equally 

 more voluminous than water, must, in order to produce the same 

 pressure, have a height of 2-31 X 1,000, or 2,310 feet to produce 

 14,7501bs. on the square inch, the requisite height will be 2,310 X 

 14,750, or 31,072,500 feet= // ; to exert 151bs. on the square inch the 

 height will be 34,550 feet =: //. Hence from the formula c :== 8 

 ^li—h' — 8 v'34,072,500 — 34,G50 = in round numbers to 4G,7ot» 

 feet per second. Now, if we suppose the vent hole to be 1-lGth of 



an inch square, its area will be-— r--of a square inch, or „ . , .. of a 



zDO 30,Bb4 



square foot, hence the quantity of the fluid escaping per second will 



be 4G,700 -rjT— or li cubic feet nearly. Thus then we see the great 



loss of power which vent holes cause, unless the action of the pow- 

 der is inconceivably rapid, and accovmt for the whole force at times 

 escaping by these apertures, when the power is over matched by the 

 resistance, a fact which frequently happens. It is to the entire obvi- 

 ation of this loss, as well as the more rapid ignition of the charge, that 

 I am disposed to allow the increase of power, and consecjuent saving 

 of gunpowder which will be caused by the use of the galvanic battery 

 in all mining and blasting operations, which athantages, coupled with 

 the perfect immunity from all danger wliich the apparatus causes, are, 

 I believe, sufficient to bring it into speedy and universal use. 



The addition of power by using a column of air is so small as hardly 

 to be taken into account, and there is no case in which I can conceive 

 it to be with any great ad\ antage employed. 



Very faithfully yours, 



June 21, 1839. J. J, 



BRITISH MUSEUM. 



(From the Times,) 



In the temporary building attached to the fifth room of the British IMuseum, 

 which contains the casts from the metopes of the Temple of Jupiter Selinus 

 in Sicily, and of which an account was given in this paper some time since, 

 one was omitted ; viz., the fifth, the execution and design of which are equal, 

 if not superior, to the others. It represents a combat between a warrior and 

 an Amazon or a divinity not known. The warrior is represented in a kneeling 

 posture, yielding to superior force ; the body, wliicli is bent, is entirely 

 covered with the leatiiern armour called ** s/x'/^/s," Two guards to represent 

 metal are adapted to protect the shoulders, and a lielt of peculiar shape 

 crosses over the left shoulder-guard, and passes down the right thigh. 

 Straps, called " ;»;7r((," are joined to the ** sjiotas" at tlie waist, and under- 

 neath is seen the tunic drawn tight by tiie position of the leg ; the scabbard of 

 the sword is suspended by the thong, *' telenum," crossing the breast. The 

 large round shield is placed behind the warrior for a relief to the figure, and 

 ]iart of the helmet is seen. The female figure has the stiff tunic and pepliim 

 in parallel folds, the earliest representation of drapery ; slie resembles in some 

 degree Minerva, whose exploits are sculptured on part of the metopes. " 

 V\ idiin tlie same apartment, placed under glass cases, in proportions of half 

 an inch to a foot, are four models of what are vulgarly called Trevetby 

 stones. As the monuments of which these are the exact representations are 

 by antiquaries supposed to be among the most ancient remains of human 

 labour uqw existing in our island, a brief account of them may not be unag- 



