1813.] Analysis of the Chinese Gong. 209 



mended the crack, and restored the tone of the instrument. The 

 crack, however, afterwards extended, as always happens in brittle 

 and very elastic bodies. 



Every body, I presume, knows that the gong is used as a kind 

 of substitute for a bell ; that the tone is at first low ; but that, 

 by skilful beating, it becomes higher and higher, till it makes 

 the whole house shake with the loudness of its tones. 



One of the most remarkable circumstances belonging to the 

 gono- is its specific gravity. I found it 8*953. Upon taking the 

 specific gravity of a piece of British bell-metal I found^it 8*368. 

 This however, was a much more complicated alloy than the 

 Chinese <rong. I found it composed of copper, tin, lead, and 

 zinc. The proportion of copper was nearly the same as in the 

 gong ; but the other constituent, which in the gong is nothing 

 but tin, I found in the British bell-metal composed as follows : — 



Tin 10-1 . 



Zinc 5-6 



Lead 4-3 



20-0 



The gong is composed (very nearly) of 80 parts copper and 

 20 of tin. The specific gravity of the purest copper I have ever 

 seen was 8'895 : but Cronstedt informs us that Japan copper is 

 of the specific gravity 9-000. Now as it is not unlikely that this 

 may have been the copper used in China for manufacturing the 

 gong, we shall suppose the specific gravity of copper to be 9'000. 

 The specific gravity of pure tin is 7*299. Now let the weight of 

 the copper in the alloy be a, and its specific gravity a; let the 

 weight of the tin be b, and its specific gravity 0. To find the 

 jH-cific gravity of the alloy, supposing no change of density, we 



have this formula: sp. gr. s '^'^l But in the present 



case « = *,« = 9-000, b = 1, and = 2*799. Hence the 

 specific gravity of the alloy ought to be 8*337 •* but it is, in fact, 

 6*953 ; very nearly equal to that of Japan copper, and higher 

 than that of any European copper I ever met with: so that a 

 very considerable' condensation has taken place, a condensation 

 amounting to more than T ' T th of the whole. This curious fact 

 hi the great inert use of density was known before, from the 

 experiments of Mr. Briche ; and, according to him, the specific 

 gravity is a maximum when the alloy is composed of 100 copper 

 and 1 b tin. When the metals are united in that proportion, the 

 isity has been found no less than ^th greater than the mean. 

 The Chinese gong contains B much greater proportion of tin than 

 16 to 100 of copper. Hence in it the increase of density is not 

 ho great as -rVtO. 



l. II. N°I1I. O 



