363 



Proceedings of the British Association. 



Mechanical Science applied to the Arts. 



The First Meeting was held on Thursday August. 



President Mr Hekxie. 



Vice-President. — Dr Lardxer. 



1. Mr Hodgkinson of Manchester detailed some experiments 

 in reference to the collision of beams and piles. This commu- 

 nication formed the continuation of a former paper read to the 

 Association. The results were, 1, That when cast-iron beams 

 were brought forcibly in contact with balls of different kinds of 

 metals cf equal weights, the deflection was the same in distance, 

 whatever the nature of the metals was. 2, That the impinging 

 masses rebounded after the stroke, through the same distance 

 under similar circumstances. 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 desti- 

 tute of elasticity. He mentioned also that wire resisted fracture 

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

 equivalent to one-third 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 pe- 

 culiar contrivance, adjusted the cardinal points so as to corre- 

 spond with the true points in the horizon ; thus obviating 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 variation of Greenwich, with a con- 

 trivance 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 exa- 

 mining flax, cotton, silk, &c. 



5. Mr Russell read a paper on the solids of least resistance, 

 in reference to steam- vessels, and related experiments which 

 tended to prove that the form of prow best suited to rapid pro- 

 gress through water, was a parabolic one. This was disputed 

 by Professor Mosely and Dr Lardner. 



