86 THE AMERICAN NATURALIST. (VoL. XXXIII. 
the andesites to one another it appears that the author proposes the 
name to cover a group of different rock types, and not as the name 
of any special type. The latites embrace all the effusive forms of 
the monzonite magmas. 
Derby + has examined a large number of specimens of kodini. peg- 
matites, and muscovitic granites and gneisses from different parts 
of Europe with respect to their rare components. In many of them 
he has discovered xenotime and monazite. 
Watson? has studied the mesozoic diabases near Chatham, Va., 
and their decomposition products, following the lines laid down by 
Merrill in the reports of his investigations on weathering. The 
changes undergone by an olivine diabase in weathering are shown 
by the first three of the following lines of figures. The fourth line 
gives the percentage of loss of each constituent in passing from the 
fresh to the decomposed condition. 
SiO. AA Fee! FeO CaO MgO Na,O KO noO Total. 
Fresh rock 45:73 X34 9.92 16.40. 3.24 47 gi = 100.78 
Weathered rock 47.87 14.43 11.55 10.45 10:56 -3-47 „61 1,02. 5 100.78 
Decomposed rock 37.09 13.19 35.69 „4I KS Ee 43. 33,83. = 100: 86 
73-64 68.19 0.00 : 98. 
The total loss is 70.31 per cent of the original, z.e. fresh, rock. 
Nitze and Wilkens ° have given us an excellent account of the 
methods employed in the gold mines of North Carolina and the adja- 
cent southern states, and good descriptions of the mines themselves. 
Their report appears as a Bulletin of the North Carolina Survey. 
Another Bulletin of this energetic and progressive survey is en- 
titled “Clay Deposits and Clay Industry in North Carolina.” It is 
by Ries,* and is one of the best reports on clay that has appeared in 
this country. It contains the records of numerous analyses, both 
chemical and mechanical, and a fine description of the special char- 
acteristics of clays of economic value. 
One of the alterative products of the paleopicrite® of Medenbach, 
- near Herborn, is sahlite. It occurs as acicular crystals imbedded in 
serpentinized olivine and as fringes of needles bordering brown 
augite, especially on that side of the augite facing olivine grains. 
A marekanite obsidian from Corinto, Nicaragua, is mentioned by 
1 pc ees Magaxine, vol. xi, p. 304. 
2 Amer. Geol., vol. xxii (1898), p. 85. 
3 pata H.B. C, and Wilkins, H. A. J. Gold Mining in North Carolina and 
Adjacent staan Regions, Bull. No. zo, N. C. Geol. ETD 1897. 
4 Bull. No. 13, N. C. Geol. Survey, 1 
5 5 Brauns, R. wae, es Jahrb. FE m etc., ok ii 41898), p- 79: 
