Geology and Mineralogy. 163 



6. Syenite and Gabbro hi Essex County, Massachusetts. — 

 Dr. M. E. Wadsworth has an article on this subject in the Geolog- 

 ical Magazine for May last. It describes the coast from Salem to 

 a point beyond West Manchester as occupied by a typical reddish 

 or grayish syenite. The granite of the same region, according 

 " to the preponderance of evidence, is the younger rock, unless it 

 is cotemporaneous with the syenite." A gneissoid schist on 

 Woodbury's Point contains " gabbro" in masses — called "irregu- 

 lar dikes " — approximately pai-allel to the foliation of the schist. 

 The "gabbro" varies from a whitish rock consisting of feldspar 

 with " a few grains of diallage " to one in which the feldspar and 

 diallage are in nearly equal proportions, and in some of it the 

 latter ingredient is in individuals two or three inches long;. Zir- 

 con-syenite similar to that of Marblehead occurs also on Salem 

 Neck, containing sodalite and elseolite. 



7. Thermal effect of the action of aqueous vapor on f eld- 

 spathic rock (kaolinizatioyi). — Dr. Carl Barus discusses this ques- 

 tion mathematically, after some careful experiments, in a paper 

 published in the School of Mines Quarterly, November, 1884. A 

 definite result was not reached ; yet the discussion is one of much 

 interest, as the author states in conclusion, " showing in how far 

 very small increments of temperature, increasing continuously, 

 through infinite time, are accurately measurable;" and "contain- 

 ing the first direct attack upon physical problems of this charac- 

 ter, many of which have an important bearing on geological and 

 metallurgical subjects." 



8. New localities of Erythrite; by Wm. P. Blake. (Communi- 

 cated.) — There are two localities of erythrite in the West which 

 deserve mention. One of these, lately opened near Lovelock's 

 station on the Union Pacific Railway in Nevada, has yielded con- 

 siderable quantities of nickel and cobalt ore. The cobalt bloom 

 occurs in crusts and aggregations of very small crystals in the 

 seams of a calcareous rock, containing also brilliant brass yellow 

 acicular crystals of raillerite. The ore as mined and shipped con- 

 tains an unusually high percentage of both nickel and cobalt. 

 There ai*e also masses of a black earthy aggregate consisting 

 largely of black oxide of cobalt. These masses do not appear to 

 carry manganese oxide in any appreciable quantity and can not 

 properly be referred to the ores of manganese, as with asbolite, 

 but are rather entitled to a separate place as black oxide of cobalt, 

 for which the name " asbolite " may be retained if the description 

 is amended so as to make the presence of manganese unessential. 



The other locality is in Los Angeles County, California, at the 

 Kelsey Mine, Compton, where the erythrite is associated with an 

 ore of silver and of cobalt in dark-colored earthy masses in a 

 gangue of heavy spar. This occurrence was noted in 1881 and is 

 described in the Report of the State Mineralogist of California 

 for 1882, p. 207, and in the fourth report, p. 179. 



