20 Mr. B. Bevan on the Modulus of Elasticity of Gold. 



distance), it is contrived, by performing this experiment at a 

 small distance from contact, satisfactorily to show the difference 

 of power. Observe what weight the magnet is capable of 

 raising from a small distance; say ^ an inch, — and vary the di- 

 stance until by a few trials you find what is the exact distance 

 it lifts the given weight at the moment the poles are reversed, 

 and that it will not have power to lift more. Now keep the 

 weight this exact distance from the magnet by means of a bit 

 of glass or wood placed between ; the weight must now be 

 considerably reduced before it can be suspended at this di- 

 stance from the magnet when the poles are stationary, and 

 the difference of weight will show the power of the magnet 

 under both circumstances. 



Dublin, March 16, 1833. P. M. 



VI. On the Modulus of Elasticity of Gold. By B. Bevan, Esq. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 

 QINCE my former communication on this subject, I have 

 ^ procured a prismatic bar of gold of the standard quality 

 used in British coinage, and have found the modulus of elasti- 

 city in one direction to be 12,226,000 pounds, and in the other 

 direction 11,955,000, — the mean of the two is 12,110,500 

 pounds; from which the height of the modulus will be found 

 about 1,480,000 feet. The additional height of the modulus 

 of coinage gold above that of pure gold is less than I expected; 

 it agrees, however, very nearly with the calculated modulus, as 

 deduced from the proportioned modulus of gold and its alloy. 

 This result suggests an important inquiry on the properties of 

 alloys in general, and is deserving of the attention of the ex- 

 perimentalist. This inquiry led me to the modulus of copper: 

 this metal is given in the Supplement to the Encyclopaedia 

 Britannica 5,700,000 feet, which I find upon examination 

 to be erroneous: upon whose authority it is quoted I am not 

 aware. My experiments, repeated with considerable care, give 

 4,380,000 feet, or nearly three times the height of that of gold. 

 Investigations of the law that governs combinations of dif- 

 ferent metals may be readily tried with various proportions of 

 zinc and lead, — two metals of easy fusibility, and of great dif- 

 ference of elasticity. Compositions of lead and tin may also 

 be employed for this purpose. 



I am, Gentlemen, yours truly, 



B. Bevan. 



