436 
POPULAR SCIENCE REVIEW. 
microscopic crystals in tlie same form, belonging to the regular system, as 
the periclase of Vesuvius, pyrochroite (MnO,H 2 0), also crystallized, haus- 
mannite, manganese spar, brusite, heavy spar, as well as hornblende and 
granite. T. Nordstrom publishes an analysis of vanadinite, now for the 
first time found in Sweden from the Undenas (manganese) mine in West 
Gothland, and a mineral containing 5 per cent, of selenium from Fahlun. 
Selenium has been found in the sulphuric acid mud of Fahlun ; but 
minerals containing this substance are very jare. G. Lindstrom describes 
Thoumasite , a new mineral species from Areskutan in Jemtland, which 
has the following curious composition — 
0a0,Si0 2 + CaO,C0 2 + 0a0,S0 3 + 14H 2 0. 
Great Meteorite in Iowa. — Professor Peckham, in a letter to the editor of 
“ Silliman’s Journal ” (July, 1879, p. 77), gives an account of the fall of a 
meteorite at 5 p.m., on May 10, at Estermills, Emmet County, Iowa. One 
fragment, weighing almost 500 pounds, fell on railroad land and buried itself 
14 feet in stiff clay soil. Another portion, of about 170 pounds, fell on a 
farm at a distance of about two miles from the above. Smaller pieces, from 
a few ounces to several pounds in weight, were scattered in the vicinity. 
The fall was accompanied by a noise described as a continuous roll of 
thunder, associated with a crackling sound. The smaller fragment above 
mentioned is of an irregularly quadrate form, measuring about 15 x 18 
inches, and 6 inches thick on an average. The metallic portion consists of 
an alloy of iron, nickel, and tin. A small piece of the metal polished and 
etched showed the Widmanstattian figures very finely. Half the mass is stony 
matter, consisting of dark green crystalline masses, imbedded in a light grey 
matrix. When the whole is powdered, a violent reaction ensues on the 
addition of hydrochloric acid, and this is increased by boiling, when all but 
the grey matrix is dissolved. Under the microscope in thin sections, 
olivine and a triclinic felspar appear to be imbedded in a matrix of 
pyroxene. 
PHYSIOS. 
Absorption of TJltra-Violet Radiations by the Atmosphere . — M. Cornu 
read a paper on this subject before the Academy of Sciences in June. He 
showed that the probability of the solar spectrum extending beyond what 
can now be seen, is evidenced by its abrupt and sudden termination in 
photographs of the most refrangible end, as compared with the spectrum of 
iron vapour. He demonstrated the atmospheric absorption by introducing 
a tube 4 metres long, closed at the ends with fluor spar, between the col- 
limator and prism. When the tube was full of air, line 32 of the Alu- 
minium spectrum is not visible, but as a vacuum is produced, the line 
appears. 
The Friction of Fluids. — Professor Unwin, of Cooper’s Hill College, re- 
cently read a paper on this subject before the Physical Society. He premised 
that it had long been known that a board, dragged through water, suffers a 
resistance varying in some way as the square of the velocity ; that a stream 
