400 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[OOTOBKR, 



manists tliemselvps, at least intelligent and educated ones, would 

 now be ashamed of. The Society's organ, Tlie Ecclenwlogist, is 

 now vastly laudatory towards that ultra-Roman Catliulic gentleman 

 Mr. A. \V. Pugin, whom it styles " the great master of Christian 

 device," albeit the specimen of his talent wliich calls forth that eulogy, 

 vix. the " new and beautiful seal" of the Camden Society, is by no 

 means remarkable for either taste or ingenuity of design, or fur aught 

 so much as the conspicuous introduction of that symbol of Romanism 

 — the "Mother of God and the Infant;" the very ostentatious adop- 

 tion of which, under their own band and seal as it were, is either ex- 

 ceedingly bold or exceedingly indiscreet, and sufficient to convict 

 them either of both temerity and effrontery, or else of besotted 

 stupidity. 



I remain, &c., 



S.P. 



AREAS OF CUTTINGS AND EMBANKMENTS. 



Sir, — In the August number of your excellent Journal there is an 

 article, taken from the Journal of the Franklin Institute aud written by 

 me, on Short Methods of Calculating correctly the Sectional Areas of 

 Excavations or Embankments, in copying the illustration of which an 

 error has been made, which may cause difficulty in demonstrating the 

 rules. In the Journal of the Institute the irregular pentagon is divided 

 into four triangles, by dotted lines drawn from the point marked f to 

 the points a and c, but in the copy the position of the lines is reversed, 

 and they are incorrectly drawn as 6 e and 5 g, which division of the 

 figure is not applicable to the purpose intended. 



Respectfully yours, 

 Philadelphia, U. S. of America, S. W. Roberts, C. E. 



Sept. 1 IM, 1844. 



We have given the diagram corrected together with the rule. 



Multiply the extreme width of the excavation, or embankment, 

 measured horizontally, by one-half of the depth at the centre; multi- 

 ply the sum of the depths at the sides, by one-fourth of the base line, 

 or bottom width (e. g.J — the sum of these products will be the sec- 

 tional area required. Thus, in the following diagram the centre stake 

 standing at b : 



C 



0* X */) + („-^+7^x'f )= Sectional Area of a 6 c g/e. 



The diagram in this position represents an excavation, by inverting 

 it au embankment. 



RAILWAY KEYS. 



Sir, — The drawing of my hollow iron keys, which is given in your 



last number, is calculated to 

 produce an erroneous im- 

 pression as to one of the great 

 advantages which they pos- 

 sess over modern keys. In 

 your drawing you have 

 shown the key as only fit- 

 ting into the upper pin 

 the of rail. In the en- 

 closed sketch you will per- 

 ceive that they fit into both the upper and lower fins, and this gives 

 them a great advantage as joint keys, for the key being elastic the 

 driving causes the contact with the rail to be very perfect, and the metal 

 being hard no unevenness of the joint, or canting of the joint chair can 

 take place, which is one of tlie great evils felt with wooden keys, for 

 here the wood being coni[)aratively soft and soon affected cy abrasion, 

 also the hold of the key on the rail being subject to great variation 

 and shrinking of the wood in wet and dry weather, the joint chairs 

 become canted and the two ends of the rails out of level, which not 

 only interposes with the comfort of travelling from the noise made in 

 passing the joints, but produces unnecessary wear and tear in the en- 

 gines and carriages, and increases the labour of repairing the road. 

 About tvfo miles of the Midland Railway, that is four miles of sin- 



gle line, in the neighbourhood of Rugby, which has been laid with 

 these keys, show a remarkable difference in the steadiness of the 

 road and the quietness of the joints, as compared with the wood keys. 

 It has been laid about six months, and the keys maintain their posi- 

 tion and hold on the lail as firmly as the first day they were put in. 



The hollow iron keys require rather more care and accuracy in 

 laying the road than the wooden keys, but in other respects they are 

 quite as easy to use, and drive readily into their places with the com- 

 mon keying hammer ; however, I must not say too much in favour of 

 my own invention; several engineers are now making trial of these 

 keys, and we shall probably in a few months learn tlieir opinion of 

 them. 



Your obedient servant, 



W. H. Barlow. 



It 



H ill- 



EXPLOSION OF HARDENED STEEL. 

 By John M. Batchelder. 

 is well known that dies, and all articles of solid steel, are very 

 liable to become fractured at the edges, if 

 made too hard, but an actual explosion, as 

 detailed below, is, I presume, of rare occur- 

 rence. The annexed figure represents a 

 fragment of a step for an upright shaft, made 

 of round steel lith inch in diameter, with a 

 hole Jth of an inch in diameter, passing 

 through the centre. 



Twelve pieces were cut from the bar, and 

 ~ after being finished in the usual manner, were 

 tempered separately, each being heated to a 

 cherry-red heat, and plunged in water until 

 perfectly cold : they were then laid aside, 

 where the temperature was at sixty-five de- 

 grees. In about an hour, one of them burst 

 into two parts, with a report as loud as that 

 of a pistol ; one of the pieces was thrown about twelve feet, the other 

 struck the wall of the shop two or three feet distant. Of the whole 

 number made, eight were broken at intervals of several days, but 

 without any violent explosion. Examined with the microscope, the 

 steel appears distinctly radiated, or fibrous, to the depth of a line from 

 the external surface, while the iuside is granular, but without the 

 slightest appearance of flaw, or want of actual contact of the particles 

 at the point ruptured, previous to the explosion. The specific gravity 

 of the bar-steel in 7'825; that of the fractured pieces 7-850. 



The cause of the fracture is, probably, the same as is observed in 

 the glass toy called Prince Rupert's drops, made by pouring melted 

 glass into cold water! the outside is suddenly contracted, wliile the 

 particles in the interior, cooling more gradually, assume a dittereut 

 crystalline form, and burst asunder as soon as the cohesion of the ex- 

 ternal coating is destroyed. — Franlkin Journal. 



A TRIANGULAR COMPENSATING PENDULUM. 



The problem of a compensating pendulum, made of a single piece 

 of metal, occupied my attention several years ago . the subject passed 

 from my memory, but was recently revived by looking over some old 

 memoranda — a copy of one of which is subjoined. Besides other 

 objections, an impression that an instrument, like the one proposed, 

 would be of too awkward a shape to be adopted in practice, induced 

 me to lay thi- project aside. The principle is, however, applicable to 

 other matters ; if, therefore, nothing of the kind has been suggested, 

 and the idia be deemed sufficiently novel to be worth recording, you 

 will, perhaps, give it a place in the Franklin Journal. 



Let the distance from C to D, be the required length of a pendulum, 

 C being the point of suspension, and D, tke oscillating body ; it is 

 required that the distance between them shall remain the same under 



all changes of temperature. 

 Now, instead of directly con- 

 necting C, D, by a straight rod, 

 (with the use of which the con- 

 dition premised is in incompat- 

 ible,) let a triangle be formed 

 as in the figure, of a piece of 

 iron, steel, or other wire, of a 

 1^ uniform thickness and density. 



It is obvious an increase of heat will lengthen the sides, A, B, and 



