220 Proceedings of the Biitish Association for [Sept. 



was. 2. That the impinging masses rebounded after the 

 stroke, through the same distance under similar circum- 

 stances. 3. These effects are not in any way dependent on 

 elasticity, but are the same as theory would point out to be 

 the consequence of the collision of bodies destitute of elasti- 

 city. He mentioned also that wire resisted fracture most 

 effectually, when it was extended by means of a weight, 

 equivalent to ^ of the weight required to break it. 



2. Mr. Mallet read a paper on the fracture of bars of 

 cast iron. 



3. Mr. Ettrick read an account of a compass which, by 

 a peculiar contrivance, adjusted the cardinal points so as to 

 correspond with the true points in the horizon : thus, ob- 

 viating the necessity of allowing for the variation. This 

 effect was produced by securing the needle upon the card 

 by moveable clamps, and adjusting it for the magnetic va- 

 riation of Greenwich, with a contrivance for altering it in 

 situations where the local variation was different. 



4. Mr. Pritchard shewed an achromatic microscope, in 

 which the angular aperture of the object glasses exceeds 

 any that have, hitherto been constructed. It is peculiarly 

 serviceable in examining flax, cotton, silk, &c. 



5. Mr. Russell read a paper on the solids of least resist- 

 ance, in reference to steam vessels, and related experiments 

 which tended to prove that the form of prow best suited to 

 rapid progress through water, was a parabolic one. This 

 was disputed by Professor Mosely and Dr. Lardner. 



6. Mr. John Taylor stated that by calculating from the 

 duty on steam engines in Cornwall, it appeared, that work 

 performed by means of 1 bushel of coal, required 10 or 12 

 years ago 2 bushels ; and, in the time of Bolton and Watt's 

 patent 4 bushels were necessary, while at the commence- 

 ment of the use of steam power, the coal required was 16 

 bushels. The steam engines at present in Cornwall were 

 equal to 44,000 horse power. 



7. Dr. Lardner made some observations on Rail Roads. 

 He stated that every road offers a sensible resistance to 

 traction, but this on a rail-road is less, because the surface 

 is more uniform. The resistance on a rail-road to the 

 power of traction is always the same, as the resistance pro- 

 duced by ascending an acclivity, rising 1 foot in 250 ; that 



