480 Scientific Intelligence. 



Co., Georgia, has recently been brought from some Colorado 

 locality. For its power of absorbing liquid it is quite remark- 

 able. When water is allowed to slowly drop on it, it first 

 becomes very white and chalky, and then gradually, perfectly 

 transparent. This property is developed so strikingly that the 

 finder has proposed the name " Magic Stone " for it, and has 

 suggested its use in rings, lockets, charms, etc., to conceal pho- 

 tographs, hair or other objects which the wearer wishes to 

 reveal only when his caprice dictates.' The specific gravity of 

 several specimens was taken with the following results : — Nos. 

 1-3 were slabs 2 mnL thick, No. 4 was a natural lump with glazed 



"Water abs. Weight(in water). Spec. grav. 



coating. 







Dry. 



Wet. 



Water abs 



Grams. 



Grams. 





1. '880 



1-342 



•588 



2. -644 



•934 



•416 



3. -730 



1-109 



•379 



4. 1-8745 





1-0595 



•463 



2-110 



•3385 



2-091 



382 



2-097 



'864 



2-191 



The weight was taken both dry and wet, and it will readily 

 be seen that this hydrophane absorbs more than an equal vol- 

 ume of water. 



A remarkable nugget of Silver. 

 Gen. A. G. Greenwood recently called my attention to a 

 nugget of native silver weighing 606^- ozs. Troy, one of sixty 

 that have been found at the Greenwood group of mines in the 

 state of Michoacan, Mexico. The other nuggets weighed from 

 one to thirty-five pounds each. The large nugget is entirely 

 worn except in cavities where some of the crystals are rounded 

 and the form is still visible. It is almost pure silver, scarcely 

 a trace of any gangue rock being discernible. This specimen 

 was found on the surface, and in its original state is said to have 

 weighed 12 lbs. more. It is one of the most remarkable nug- 

 gets of silver ever found. The geological formation is a lime- 

 stone with outcroppings of limonite. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Study of Chemical reactions by means of the Elec- 

 trometer. — Bouty has sought to make use of the electric resist- 

 ance of solutions in order to determine the chemical changes 

 produced when two dissolved salts are mixed together. Thus, for 

 example, when potassium sulphate and sulphuric acid are mixed 

 in solution, the observed resistance is greater than that calculated 

 on the supposition that no action takes place between them. 

 Hence it follows that the normal salt combines with the acid to 



