NATURAL SCIENCES OF PHILADELPHIA. 13 



111 order not to spoil the specimen, I took only 0.1 gramme for 

 analysis, and in this quantity could not obtain anj' other reaction 

 but on zinc. This metal was first precipitated by ammoniac 

 sulphide, then redissolved and precipitated by sodic carbonate. 

 It- weighed, after ignition, 0.09.5 gramme. Tiiis result leaves no 

 doubt of the truth of the assertion, that the substance examined 

 is pure oxide of zinc. 



Placed under the microscope, with a magnifying power of 250 

 diameters, the needles present a purely prismatical habitus. 

 Moreover, it seems apparent from the form of the basal termina- 

 tion, that the prisms belong to the hexagonal system. 



The natural oxide of zinc, the zincite or red zinc ore, has not 

 been found 3'et in well-defined crystals; but the massive specimens 

 of Sparta, Franklin and Stirling, N. J., show a distinct cleavage 

 after a hexagonal prism and after the hexagonal basis. Thus, the 

 identity of form in the natural oxide of zinc and in the artificial 

 oxide, would seem to be existing. 



On a Boiler Incrustation from Neiv Jersey. By George A, 

 KoENiG, Ph.D. Some time ago Mr. Joseph Harrison, Jr., pre- 

 sented to the Academy a specimen of boiler incrustation from 

 Orange Co., N. J. The physical properties of this incrustation 

 were remarkable enough to suggest a chemical examination. It 

 was about half an inch thick, presented a smooth surface, was 

 hard and coherent, of a brownish-flesh-color, and showed on tlie 

 fracture a distinct prismatic structure, the prisms standing 

 vertically on the surface. It looked very much like tlie so-called 

 " Sprudelstein" from Karls!)ad in Bohemia, which is aragonite. 



The analysis gave the following results : 



99.57 



57.58 parts of sulphuric acid require, by theory, 40.306 parts of 

 calcic oxide to form calcic sulphate, which latter number corres- 

 ponds perfectly' with the one found ; we can say, hence, that the 

 incrustation is composed of 



Calcic sulphate = 97.89 



Ferric hydrate = 0.72 



Silica 0.05 



Organic matter 0.82 



To m}' knowledge there has not been described, so far, a boiler 



