470 Scientific Intelligence. 
Rocksalt ‘pit its own rays more strongly than those of 
other bodie 
The abso onption increases as the difference in temperature be- 
tween os radiating and absorbing rocksalt sae diminishes 
The absorption eaities its full value when the difference in 
temperature between two such plates is nothing. Baur does not 
believe with Magnus that the radiations from rocksalt are homo- 
geneous; but concludes that long waves are accompanied more or 
less with longer and shorter waves, just as a yellow glowing solid 
body sends forth not only yellow but also radiations of a greater 
wave length.— Annalen der Physik und Chemie, No. 5, ise be. 
ii-21, 
6. Application ow Organic acids to the Hxamination of “Min: 
erals, No. 3; by H. Carrinaton Borron, Ph.D.—Professor Bol- 
ton has continued his investigations as to the action of organic 
acids on minerals, and obtained some additional seats of interest. 
‘The acid e mploye d was citric acid, which, as the author has shown, 
has a power.of decomposing minerals little less than that of hydro- 
chloric acid; the effect of prolonged action at ordinary tem 
atures was especially considered. Of the sulphides, chalcocite 
showed signs of decomposition at the end of ten days, and after 
several months a partial solution of a green color was obtained; 
pyrite was slightly attacked in eight days, and a month later a 
solution of a reddish-yellow color was obtained ; chalcopyrite 
acted similarly, one ® gra m lost 11 per cent after fo urtee en mont 
onite were experimented upon and found to be strongly attacked 
in eight days, hematite yielded more slowly, showing decided 
decomposition after several months. Of the silicates, datolite 
was most quick Rt tay are ielding gelatinous silica after 
vianite and perpeniine were decided] y decomposed in eight days, 
sina The fe spp were unequally etackelt under like condi- 
tions, labradorite yielded most easily, orthoclase and oligoclase 
showed marked signs of decomposition after eight months, while 
albite is still doubtful. Tourmaline and staurolite yielded after 
four or five months, while tale and cyanite seemed to resist attacks. 
Muscovite and biotite ‘puro a slowly, the latter showing signs 
of decomposition the soon The author gives a table which 
nite, sdgeiiekt e, gypsum (2); those very slowly dee bby ‘are 
orthoclase, oligoclas e, albite ° (®), biotite, muscovi nes tourmaline, 
staurolite, hematite ; not dec omposed are quartz, corundum, ga 
beryl, fluorite, barite, tale (?), eyanite (?). The author su 
