INDUSTRIAL PROGRESS DURING THE YEAR 1875. cclxxxix 



and give the following tabulation as the correct expression 

 of the relative value of several lights examined, in which the 

 intensity increases with the figures : 



Relative Chemical 

 Energy. 



Drummond-light 3 



Zinc burning in oxygen 4 



Magnesium lamp 5 



Flame of nitrous oxide and carbon-disulphide vapor 6 



Flame produced by leading nitrous oxide into that of carbon- 

 disulphide burning in an open dish 6-7 



Flame produced similarly by oxygen 7 



Oxygen directed upon the flame of burning sulphur 8 



From the foregoing it appears that the light produced by 

 the combustion of sulphur in oxygen is possessed of extraor- 

 dinary chemical energy, and may be applied to photograph- 

 ic uses w T ith excellent effect. 



Stein, in a communication upon the subject of normal 

 weights and measures of rock-crystal, remarks that Kekule 

 pointed out, some time ago, the fact that all amorphous 

 bodies, whether produced by casting, rolling, hammering, or 

 stamping, are possessed of the tendency to go over into the 

 crystalline condition. The molecules of such substances 

 he regards as being in abnormal positions relative to each 

 other, and the striving toward crystallization is the natural 

 effort to assume the position of equilibrium. For these rea- 

 sons, Kekule objected to normal weights and measures made 

 of metal, affirming that they could not be relied upon to re- 

 main constant ; while, on the contrary, this objection would 

 not hold good of such normals when constructed of a crys- 

 tallized substance, as, for example, of rock-crystal. Recog- 

 nizing the validity of the foregoing arguments, the author 

 has had such weights and measures cut at Oberstein. To 

 produce the measures, the pieces are cut exactly parallel 

 with the optical axis of the rock-crystal, so that the main 

 axis of the crystal coincides with the median line of the rod. 

 The same rule is likewise observed with the weights, by 

 which an unequal expansion is avoided. These normal 

 weights and measures are manufactured at Oberstein by H. 

 Stern, who has likewise devised a method of attaching the 

 pieces to each other, wdien measures of considerable length 

 are required, in such a manner that any alteration of the 



13 



