322 Royal Society. 



Pyramidal : 



1, 1 1 = 50° 2'7. 

 Observed forms : 



1, 10 2, 10 4, 3 4, 2 1, 112, 114, 



with very obscure traces of the forms 



5 2, 4 ], 2 3. 



The combination most frequently observed was 



1, 2 1, 112. 



The angles between normals to the faces, computed from a mean 

 of the best observations, are — - 



1, 



1 



4 



= 



/ 



16 37 



1, 



1 



2 



= 



30 50 



1, 



2 



3 



= 



38 31 



1, 



3 



4 



= 



41 50 



1, 



2 



1 



= 



67 16 



1, 



5 



2 



^z 



71 28 



1, 



4 



1 



^^ 



78 10 



1, 



1 



1 4 



— 



22 53 



1, 



1 



1 2 



— 



40 10 



2 1, 







2 1 



— 



81 25 



1 1 2, 



1 



1 2 



HZ 



54 16 



2 1, 



1 



1 2 



' 



44 17 



The faces of the form 1 are large and bright ; those of all the 

 other forms are extremely narrow, and are usually uneven. 



Cleavage 1, very perfect. 



No other forms of crystals than those just described were observed 

 in any of the alloys experimented with. 



The largest and best-defined crystals were obtained from the alloys 

 containing about 41 per cent, of gold. The plates were sometimes, 

 when crystallized from 300 grms., about 30 millims. long and 15 

 millims. wide, being the width and depth, of the alloy in the 

 crucible ; they were generally of a bronze colour, proceeding from a 

 slight oxidation of the tin : their true colour was that of tin. All 

 the alloys emit a grating sound when cut through, as tin does, and 

 are all exceedingly brittle. 



From the above experiments it appears, first, that the well- 

 defined crystals are not limited to one definite proportion of the con- 

 stituents of the alloy, but are common to all gold-tin alloys con- 

 taining from 43 to 2.7*4 per cent, gold; secondly, that crystals and 

 mother-liquor are never of the same composition. These facts coin- 

 cide with those found by Cooke* in his research on tin and anti- 

 mony alloys, who observed that zinc and antimony are capable of 

 uniting and producing definite crystalline forms in other proportions 

 than those of their chemical equivalents. 



" On the Sensory, Motory, and Vaso-Motory Symptoms resulting 

 from the Refrigeration of the Ulnar Nerve." By Augustus Waller, 

 M.D., F.R.S. 



* Silliman's American Journal, (2) vol. xx. p. 222. 



