specific Gravity , and comparative Wear of Gold. 159 
Table IV. ( continued .) 
1 
Quality. 
Weight be- 1 
fore friction. | 
1 
Weight after 
friction. 
1 
Loss. 
1 
Grains. 
Grains. 
Grains. 
41. Gold with silver and copper 
141 
139,90 
1,10* * * § 
42. Gold with iron and copper 
137*50 
135,90 
1,60 
43. Gold with copper 
138,40 
136,9° 
1,5° 
44. Gold and copper in equal 
parts - 
103,14 
103,10 
,°4+ 
45. Gold with copper 
141 
140 
i,° I 
46. Gold with tin and copper 
144>50 
I38 
650 
4 7. Gold with copper, cast in 
-sand - 
135*40 
132.80 
2,60 
48. Gold with iron and copper 
135,80 
133,80 
2,0 
49 . Gold with copper, cast in 
sand - - - 
136>03 
136 
0,03 
50. Gold of 18 carats 
1 25*3 8 
125,30 
0,08 
51. Gold with iron and copper 
137,40 
13 6 *,50 
0,90 
52. Gold with tin and copper 
141,80 
136,70 
5,10 
53 Gold with tin and copper 
140,90 
139,20 
1,70 
54. Gold of 18 carats - 
125,02 
125,30 § 
— 
* The gold alloyed with silver and copper was coated by the gold alloyed with iron 
and copper. 
f The gold alloyed with an equal part of copper was coated by the gold made 
standard with copper. 
J The gold alloyed with copper was coated by the gold alloyed with tin and copper. 
§ Increased in weight 0,28. 
The above effects sufficiently show, that the more ductile metals are always worn 
by those which are comparatively harder ; and, in every experiment, it was constantly 
observed that the latter became coated by the metal of the former. This coating was 
commonly spread thinly over the surface ; but, in some few instances, (especially when 
a very hard metal rubbed against one which was very soft,) the particles of the latier, 
instead of being spread over the whole surface, became accumulated, so as to form 
little protuberances or knobs. 
