168 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[May, 



On all the otlier wlieels describe evoliite circles, bearing the same proportion 

 to their respective pitch circles, which the evolutc circle of the smallest wheel 

 bears to Us pitch circle — thus, if in the smallest wheel the evolute circle is 

 ^th less than the pitch circle, let .ill the other evoliites be -Jjth less than 

 Iheir pitch circles. From these evolntc circles as bases, describe the involute 

 curves of the teeth, making the curves pass through the points set out for the 

 teeth, upon the pitch line. 



" An Account of some Experiments to determine the force necessary to 

 punch holes throuijh plates of vrowjht iron and copper." By Joseph Col- 

 thiirst. 



These experiments were performed with a cast-iron lever, 11 feet long, 

 multiplying the strain ten times, with a screw adjustment at the head, and a 

 counterpoise. 



The sheets of iron and copper which were experimented upon were placed 

 between two perforated steel plates, and the punch, the nipple of which was 

 perfectly llat on the face, being inserted into a hole in the upper plate, was 

 driven through by the pressure of the lever. 



The average results of the several experiments (which are given in a de- 

 tailed tabular form) show that 



Hence it is evident, that the force necessary to ])unch holes of different 

 diameters through metal of various thicknesses, is directly as the diameter of 

 the holes and the thickness of the metal. 



A simple rule for determining the force required for punching, maybe thus 

 deduced. 



Taking one inch diameter, and one inch in thickness, as the units of cal- 

 culation, it is shown that 150,000 is the constant number for wrought-iron 

 plates, and 96,000 for copper plates. 



Multiply the constant number by the given diameter in inches, and by the 

 thickness in inches ; the product is the pressure in pounds, which will be 

 required to punch a hole of a given diameter, through a plate of a given 

 thickness. 



It was observed, that duration of pressure lessened considerably the ulti- 

 mate force necessary to punch through metal, and that the use of oil on the 

 punch reduced the pressure about eight per cent. 



A drawing of the experimental lever and apparatus accompanied the com- 

 munication. 



" Geological Sections of Railway Cuttings." By Mr. Sopwith. 



Mr. Sopwith called the attention of the meeting to the valuable Geological 

 Sections presented by the railway cuttings, and other engineering works now 

 in progress ; this was particularly the case on the North Midland Railway, 

 where the crops of the various seams of coal, with the interposing strata, 

 were displayed in the clearest manner, developing the geological structure of 

 the countiy which the railway traverses. Numerous similar instances induced 

 the British Association to devote a sum of 200/. (which it was bcUeved would 

 be increased from other sources), for obtaining authentic records of such 

 sections, before the action of the atmosphere or the progress of vegetation 

 should have obhterated the instructive pages of geology, which the engineer 

 had opened to view. 



The Committee of the British Association, especially charged with this sub- 

 ject, were desirous of bringing it before the Institution of Civil Engineers, for 

 the double purpose of receiving from its Members those suggestions which 

 they are so competent to give, and of obtaining from them that powerful aid 

 and co-operation which the practical nature of their engagements so essen- 

 tially enabled them to afford ; it was accordingly suggested, that the Council 

 should receive from Graduates, descriptive papers and measured deUneations 

 of sections, as their communications previously to their Election. Much 

 assistance might thus be rendered, and the contributions, after having been 

 read at the Institution, might be added to the general series preserved in the 

 Museum of Economic Geology, which under its present able direction is be- 

 coming daily more interesting both to the engineer and the geologist. 



Mr. Sopwith exhibited a specimen of a blank chart, prepared by Mr. 

 rhillips, of York, for the committee. It consisted of a sheet engraved in 

 squares, on a scale of 40 feet to an inch, containing a space equivalent to 800 

 feet in length, and COO feet in height, upon which it was proposed to delineate 

 the sections in their true vertical and horizontal proportions ; the base line 

 representing either the level of the sea at half tide, or the datum line of the 

 railway, as might be most convenient. There would remain in every case a 

 large portion of the sheet unoccupied by the section, and upon this it was 

 proposed to exhibit, on a magnified scale, the details of the section ; the fos- 

 sils and other organic remains might also be shown, as the divisions of the 

 squares would enable the sketches to be made of any dimensions in correct 

 proportions. .\n example of these charts had been prepared bv Mr. Phillips, 



giving a section of a ilee|i cutting on a railway, the enlarged portion exliibit- 

 ing the details of the strata at two particularly interesting points, as also of 

 the specimens of sigillaria, stigmaria, &c. in that formation.* 



Geological Models. — Mr. Sopwith also laid before the meeting a set of 

 models, which were intended as hand specimens for the purpose of familiarly 

 explaining faults, slips, or dislocations of the strata, and other geological 

 phenomena, which could not be clearly demonstrated without such assistance. 

 One of these models represented the horizontal deposition of stratified rocks, 

 and the svibsequent removal or degradation of such rocks, forming valleys of 

 denudation. Another, by the displacement of the lower rocks, exhibited the 

 formation of a slip dyke, or fault, which was the "lode or vein" of the 

 mineral miner, and the "fault" or "trouble" of the collier, as these inter- 

 ruptions of the continuity of the bed of coal were generally termed, .\nother 

 model showed a succession of slip dykes disturbing the stratification, so as to 

 present the appearance of a great abundance of coal at the surface by the 

 " cropping out" or "bassetting" of a number of seams or beds of coal, whereas 

 in reality there was only a repetition of the same beds. By examining the 

 base of the model, and also by opening it on an oblique plane nearly parallel 

 with, and at a short distance below, the surface, it would be found that there 

 was no coal at all. A fourth model exhibited the conditions under which 

 some of the largest collieries in the kingdom are wotked, namely, that the 

 seams of coal do not ajjpear on the surface, but on opening the model a ver- 

 tical section is exhibited, and the several beds are shown, disturbed as in the 

 former case by faults or dislocations, but which have not the effect of bring- 

 ing the coal to the surface. 



It has always been difficult to demonstrate w ithout the aid of models the 

 apparent form of strata, as effected by the contour of the country ; sometimes 

 the rocks form a V, pointing up the valley, and sometimes in the opposite 

 direction. General observers and even practical miners were apt to conclude, 

 that this different direction of the point of the V, indicated a different direc- 

 tion of the strata, but the models showed that in both cases the direction of 

 the strata was the same ; that in both cases the rocks were inclined in the 

 same direction as the valley, the only difference being that in one case the 

 rocks form a greater, and in the other a less, angle with the horizon than the 

 bottom of the valley. The other models exhibited the " up-cast "and " down- 

 cast" which occur in coal mining, and intersections of veins of different ages, 

 &c. Most of the specimens shown presented details of the carboniferous 

 formation, but models of this description were of course applicable to every 

 formation and to every kind of geological structure. Mr. Sopwith brought 

 forward this subject in hopes that eventually a close union and active co- 

 operation might be estabhshed between the leading scientific institutions of 

 this country, and more especially that the Geological Society and the Insti- 

 tution of Civil Engineers would unite in promotingthe progress and improve- 

 ment of geology and engineering. 



February 9. — The President in the Chair. 

 The following were balloted for and elected : Sir Charles Baird, as a Mem- 

 ber : Samuel Beazley, William Gossage, John Hughes, John Howkins, and 

 Charles Schafaeutl, M.D., as Associates. 



" Upon the Application and Use of Aiuriliary Steam Power, for the pur- 

 pose of shortening the time occupied by Sailing Ships upon distant voyages." 

 By Samuel Seaward, M. Inst. C.E. 



But few years have elapsed since the possibility of propelling vessels by the 

 power of steam was treated as a chimera ; and although the practicability of 

 its application for short voyages has been successfully demonstrated by the 

 numerous vessels plying between this country and the Continent, it is but of 

 very recent date that its employment for long sea voyages has been adopted. 

 The weight of the powerful machinery and the fuel, and the consequent loss 

 of space for cargo, together with many other circumstances attendant on the 

 present construction of steam vessels, induced the author (who received the 

 education of a seaman, and has since had extensive practice as an engineer) 

 to believe that a more efficient mode of employing steam power for long sea 

 voyages might be adopted. 



Notwithstanding the great improvements which have taken place in the 

 construction of steam vessels, and their machinery, it would appear that the 

 duration of the voyage ought not to exceed twenty days, after which time a 

 fresh sui)]ily of fuel becomes necessary ; hence, steam has rarely been adopted 

 for very long voyages. The reason of this limit to the duration of the voyage 

 of a steam vessel, as at present equipped, is that an increase of power does 

 not produce a corresponding increase of speed, while the weight of the ma- 

 chinery increases in proportion to the power employed, and in some cases 

 exceeds it ; for instance, small engines, with the water in the boilers, gene- 

 rally w eigb about one ton per horse power, while in some large engines the 

 ratio is nearly twenty-five cwt. per horse power. 



.\ quadruple increase of power will not produce double the original velocity 

 in a steam ship, although, in theory, such is assumed to be the case ; for as 

 the weight is more than doubled, the immersed sectional area becomes greater, 

 and a still further increase of power is necessary. It has been shown by ex- 

 perience, that if a vessel with a given power is propelled through the water 



Specimens of the prepared sections ai.d blank charts may be obtained 

 from Mr. Delabeche or Mr. Jordan, at the Museum of Economic Geology, 

 Craig's Court, Charing Cross, or from the Secretary of the Institulion of Civil 

 Kngineers. 



