loa 



PERREAULX DIVIDING MACHINE. 



[1852. 



of couutiy, but wc are of opinion that part of tlio project at least, 

 is premature. 



We have now, we believe, noticed all the Acts relating to 

 Railways, pa'sed dining the recent session. They embrace an 

 amount of Railway Legislation certainly unprecedented in a 

 Canadian Pai'liament, and if all the roads projected are built, 

 Canada will in no way be behind her neighboui-s in Rafli'oad com- 

 munication. It is true that some of the projects are of doubtfid 

 value, or at least, premature ; but none of them ai-e hkely to be pro- 

 ceeded with, except such are well calcidated to make a fair re- 

 turn for the capital invested. We give below a synopsis of the 

 Railroads chartered and in progress in Canada, by which it will 

 be seen that we now have 205 miles in operation; 618 miles 

 under construction ; and 1056 miles chartered. 



Peneaulx Dividing MacUine. 



A Dividing Machine by which any scale of equal parts what- 

 ever, not exceeding a certain value, can be graduated with the 

 greatest facility, or any arbitrary distance be divided into any 

 arbitrary number of equal paits, is a contrivance which offcre so 

 many facilities to scientific men, engineer.'=, draughtsmen and 

 others, that a short account of one which attracted much notice 

 at the Great Exhibition, may probably be interesting to our 



readers. The fimdameut:d part of Perreaulx machine a deviser 

 <tc., consists of a screw of exquisite workmanship, sixty centi- 

 metres in length, (23-6 inches) and of the \alue of half a 

 millimetre, nearly 0*02 inch, to one revolution. The jiecuhar 

 peifection of form, as regards straightness and imifonnity of 

 value, which the artist has attained in this vital pait, constitutes 

 one of the great excellencies of the apparatus. This screw gives 

 motion to the cai-riage to which the giwing tool, or pen is 

 attached, and is tunied by a small winch handle connected with 

 an ingenious micrometrical apparatus, which can be set with the 

 greatest facihty, so that the act of turning the handle shall cause 

 the graver to advance any line or distance required, from six 

 milhmetres, 0*2 3 6 inches, down to one-eight-hundi'edth part of a 

 milhmetre, or about the twenty-thousandth part of an inch. 

 This is effected by two cu'cles, one divided on its cu-cumference 

 into 200 teeth, the other having a thread or screw of twelve 

 turns on its circumference, and also on its face, 400 equal divisions. 

 A fixed and a moveable stop enable the operator to adjust the 

 space scale to any value from a fraction of one revolution to 

 twelve, a number limited only by the number of threads on the 

 wheel or circle above referred to. The stroke of the graver is 

 made with great delicacy by drawing out a silk cord, and there 

 is a mechanical contrivance by which every fifth stroke is made 

 longer than the othere. The arrangement by which a wheel 

 with 200 teeth on its circumference, which is the medium by 

 which the motion of the micrometer circle is communicated to 

 the screw, is made to answer the motions of a micrometer circle 

 divided into 400 equal jiarts, is very ingenious: it consists simply 

 of two rachets, one always raised when the other is down, and 

 one-half a tooth in advance of the other, — consequently one or 

 other will act at every four-hundredth part of a revolution. 

 There are two microscopes to assist the measurement of given 

 distances, but they are not requked for graduating. We may 

 illustrate the use of the machine by referring to such operations 

 as those of the Observatory at Toronto. A great proportion of 

 the instalments used at that establishment me;isure angidar 

 deviations by the principle of reflexion, that is to say, a scale of 

 equal linear values, generally a millimetre, is adjusted opposite to 

 a magnet canyuig a plane reflector, and a fixed telescope placed 

 at a convenient distance for observing the particular division of 

 the scale which is reflected from the mirror, at certain moments, 

 from which the position of the magnet is inferred. Now die 

 ano-iilar value of each division, obviously depends upon the dis- 

 tance of the scale from the reflector, and tlus must be governed 

 in many cases by other considerations than that of obtaining a 

 precisely convenient value ; the consequence has been, that all 

 sorts of inconvenient fractional units appear- in the records, adding 

 greatly to the trouble of reduction, and impeding the comparison 

 of the results vvith those obtained elsewhere. The same being 

 true of almost every similar collection of observations, the result 

 is an incredible increase to the labour of pui-suing any specific 

 enquiry through them. Every one knows what an impediment 

 the existence of different scales of the thermometer is to extensive 

 comparisons of climate or temperature, and it is easy to conceive 

 what it would become if, instead of having to deal only with 

 Fahronheil, Celsius, and Reaumeur, each register presented us 



