On Machines for measuring Elasticity. SlT 



In one of the late French journals it is proposed to sepa- 

 rate the oxicks oF cobalt and nickel by oxidizing the former 

 by means of the hvpcroxygcnized muriatic acid. I have tried 

 (he method recommended without success. 



LVIII. On Machines far measuring Elasticity. By a Friend 

 to Physical Inquiries. 



To the Editor of the Philosophical Magazine. 



j^ FEW years ago an eminent botanist, now abroad, being 

 desirous of ascertaining the comparative elasticity of diffe- 

 rent woods, was wishing to have some machine made for 

 that purpose ; but whether or not any such machine has 

 been yet made I am not acquainted. At the same time the 

 subject was mentioned the following contrivances occurred 

 to my mind, which, if carried into execution, might in 

 some measure answer the purpose ; and if you think them 

 ■worth communicating to the public, I shall be glad to see 

 them noticed in your magazine. They may serve for some 

 of your readers as hints to improve on, and be the means of 

 some much more accurate method of ascertaining the elas-» 

 ticitv of bodies being inveiTtcd. 



P'irst Contrivance. — A machine might be made which 

 should have a flap on which balls of different sorts of wood, 

 or other sub-tances, might be placed, and suddenly let fall 

 on a slab of ivory or marble : on this machine there should 

 Be an upright graduated post in order to see to what height 

 each ball rebounded ; by which, in some instances, the com- 

 ■jiarative' elasticity of the body subjected to trial might be 

 judged of. 



Observations. — This method, in order to be accurate, 

 ishould be tried in the exhausted receiver of an air-pump ; 

 otherwise with light bodies, such as cork and elder-pith, 

 both very elastic, the experiment will not answer. The in- 

 strument for performing the common guinea-and-feather 

 operation might, perhaps, be as good a contrivance as any: 

 fa wire cage might be placed under the receiver in order to 

 protect the glass. Bodies of nearly the same gravity might 

 be tried in the air. The standard ball might be ivory let 

 fall on ivory, or marble let fall on marble. 



Second Contrivance. — Thin slips of different sorts of 

 wood^ &tc. might be bent half round a circular piece of 



board. 



