1040 The American Naturalist. [December, 
shales taken from some of the deepest coal mines in Wales. The 
chemical composition of the particular shale analyzed does not differ 
materially from that of some of the carboniferous shales from other 
coal fields. Physically the deeper shales are not much more compact 
than hard clays. The author reviews the results of his observations on 
shales and slates. He states that what takes place in a rock during its 
progress from clay to shale, is the development and crystallization of 
muscovitic mica and the production of chlorite. He also calls atten- 
tion to the fact that dynamic metamorphism is made to explain many 
phenomena connected with the crystallization of slates, that are capa- 
ble of being explained better by static metamorphism. The spots of 
many contact rocks are now thought to be secretions from a mineral- 
izing solution, depositing in these spherical forms material collected 
from the rock body. By crysiallization the spots pass over into cor- 
dierite, biotite or staurolite crystals. 
Notes.—Cushing® declares that in addition to the rocks described 
by Kemp from. the eastern Adirondacks there is a system of diabase 
dykes, which are older than the monchiquites and camptonites of the 
district. 
By melting certain rock powders in the presence of reagents Schmutz’ 
has obtained aggregates of minerals which in most cases are very dif- 
ferent from those composing the original rocks. Eklogite fused in the 
presence of calcium and sodium fluride yielded a mass of meionite, 
plagioclase and glass; leucitite with calcium chloride gave a mass com- 
posed of a glassy groundmass and plagioclase; with the addition of 
sodium fluride and potassium silico-fluride it yielded scapolite, mica, 
magnetite ; with sodium chloride it produced augite, scapolite and mag- 
netite and a glass matrix. Granite fused with magnesium and calcium 
chlorides and sodium fluoride gave andesine and olivine in a ground- 
mass containing augite. Other rocks treated with other reagents gave 
analagous results, j 
As the result of a series of experiments made with the view of dis- 
covering a medium with a very high specific gravity that will not at- 
tack sulphides, Retgers® finds that the acetate and the mixed nitrate 
and acetate of thallium are both neutral toward sulphides. The for- 
mer is available for separating minerals with a density below 3. 9, and 
the latter those with a density below 4.5. 
6 Trans. N. Y. Acad. Sci, XV, 1896, p. 249. 
1 Neues Jahrb. f. Mia at., 1896, Í, p. 211. 
8 Neues Jahrb. f. Min., etc., 1896, I, p. 213. 
