﻿W. G. Brown — Crystallographic Notes. 377 



The following table from Professor Cooke's paper* will show 

 the relation of Lucasite to the other members of this group, all 

 being taken as dried at 100° : 



Si : £ : R : £ : H 



Hallite 



2 42 : 



2*41 



: 1-47 or 8 



8 



5 or 



32 



32 



20 



"Lerni" 



2-54 : 



2-50 



: 1-30 " 2 



2 



1 " 



40 



40 



20 



Pelhamite _. 



2-75 : 



2-46 



: 1-26 " 9 



8 



4 " 



45 



40 



20 



Culsageeite _ 



2-50 : 



2-66 



: 1-23 " 2 



2 



1 " 



40 



40 



20 



Jefferisite 



2-56 : 



2-53 



: 1-17 " 9 



9 



: 4 " 



45 



45 



20 



"Milbury" _ 



2-38 : 



2-74 



: 1-14 « 8 



9 



4 " 



40 



45 



20 



Lucasite 



2-75 : 



2-46 



: 0-80 " 7 



6 



2 " 



70 



60 



20 



Any attempt to deduce formulas for these minerals gives 

 complicated results, and it is evident that we are dealing with 

 a class of minerals of very similar physical properties but of 

 widely varying compositions. That they are in all cases 

 decomposition products of other minerals is very doubtful, for 

 when the mode of occurrence of these minerals is carefully 

 examined, it is difficult to resist the conclusion that in many 

 cases they are as original in their formation as the chlorites and 

 biotites and are not derived from them. The number of these 

 varieties is already formidable and is constantly being added 

 to, and it is much to be desired that a careful comparison of 

 the whole series shall be made, so as to reduce the number of 

 mineral names and to bring the survivors into a scientific 

 arrangement. 



Art. XLV. — Crystallographic Notes ; by W. G. Brown. 



Artificial Copper Crystals. 



On taking apart to cleanse and put away a cell of a Calland 

 gravity battery, which after using had been put aside and re- 

 mained undisturbed for two or three months, there was found 

 attached to the insulated wire coming from the copper plate, at 

 the point where it passed the zinc plate, a pendant mass con- 

 sisting almost entirely of copper crystals. At the place where 

 these crystals were formed, the gutta percha of the insulated 

 wire had been abraded and had come into contact with the 

 zinc plate. The crystals were quite firmly attached to the in- 

 sulated copper wire, and were also in contact with, but not 

 adherent to, the zinc plate. At the time the crystals were 

 found, the solution in the cell had evaporated to such an extent 

 that about half the deposited crystals were out of the solution, 

 and the zinc plate just touched it. 



* Cooke, Proc. Am. Acad., 18^5, p. 461. 



