174 MEMOIR OF THE LATE PROF. E. HODGKINSON, F.R.S. 



force,, the deflection of the beam will be the same, which- 

 ever body be used. 



3. The quantity of recoil in a body, after striking against 

 a beam as above, is nearly equal to what would arise from 

 the full varying pressure of a perfectly elastic beam as it 

 recovered its form after deflection. 



4. The effects of bodies of different natures striking 

 against a hard flexible beam seem to be independent of the 

 elasticities of the bodies, and may be calculated, with trifling 

 error, on a supposition that they are inelastic. 



5. The power of a uniform beam to resist a blow given 

 horizontally is the same in whatever part it is struck. 



6. The power of a heavy uniform beam to resist a hori- 

 zontal impact is to the power of a very light one as half the 

 weight of the beam, added to the weight of the striking 

 body, is to the weight of the striking body alone. 



7. The power of a uniform beam to resist fracture from 

 a light body falling upon it (the strength and flexibility of 

 the beam being the same) is greater as its weight increases, 

 and greatest when the weight of half the beam, added to 

 that of the striking body, is nearly equal to one-third of the 

 weight which would break the beam by pressure. 



There can be but one opinion as to the importance of 

 these deductions, direct from the voice of nature, made, as 

 they were, at a time when such an appeal was by no means 

 common. 



There are several interesting problems on impact, of a 

 high mathematical character, solved in this paper. In these 

 inquiries Mr. Hodgkinson is very particular in acknowledg- 

 ing his many obligations to his friend Mr. Fairbairn, 

 engineer, of Manchester, to whose labours and liberality 

 practical science is deeply indebted. 



We now pass on to notice his contributions to the Trans-^ 

 actions of the Royal Society. 



In the Philosophical Transactions for 1 840 there is an 



