338 RECORD OF SCIENCE FOR 1886. 



cally by an electric current upon the arrival of the vibration and be- 

 gins the exposure, closing again before the plate has made a complete 

 revolution. The registration attained is accurate to one twentieth of 

 a second. With this apparatus experiments were made in the permian 

 sandstone of Creusot, the granite of Montvicq near Commentry, and the 

 carboniferous sandstone of Commentry ; in the latter case in the mines, 

 beneath the surface of the ground. The results show: (1) The veloci- 

 ties of propagation are greater than by the old method ; (2) the dis- 

 turbances caused by chargesofjmwder or dynamite (up to 12 kilograms 

 of the latter) are, at equal distances, less than those produced by the 

 steam-hammer, falling through 5 meters; but even this at 500 meters 

 produced hardly more effect than stamping with the heel did at 10 me- 

 ters ; (3) at the surface the shocks are multiple, enduring ten seconds 

 at the distance of 1,200 meters; but beneath the surface there is but a 

 single shock and that of short duration, whether the mercury is in the 

 mine or at the surface. (C. R., Feb., June, 1886, cil, 237, 1290.) 



2. Of liquids. 



Joly has suggested a simple method of finding the specific gravity of 

 small, heavy bodies. The substance, which may have a weight of only 

 a few milligrams, is melted into some parafifln of known specific gravity 

 in a small dish. The paraffin and substance are then floated in a spe- 

 cific gravity solution, and from the data thus obtained the specific gravity 

 of the substance can be calculated. It is especially useful for porous 

 bodies. (Nature, March, 1880, xxxili, 455.) 



Handl has proposed to deteruiine the density of a liquid b^- measur- 

 ing, by means of a water manometer, the hydrostatic pressure which it 

 exerts at a given distance from its free surface. ( Anz. Ak. Wien., 1885, 

 148; J. Phys., May, 1886, II, V, 241.) 



Amat has devised a density pipette for taking the specific gravity of 

 liquids. It consists of a straight glass tube, graduated, to the upper 

 end of which is attached laterally a V-tube, also graduated on both 

 limbs. The standard liquid is placed in this V-tube and by means of a 

 rubber spherical cap on the upper end of the pipette the given liquid 

 maybe drawn into the main tube. Noting the height of this column, 

 and comparing it with the difference of level in the standard column, 

 the specific gravity of the given liquid may be read off in terms of the 

 standard. A small correctionmay be made for capillarity. Theresults 

 are accurate. (Bull. Soc. Chim., May, 1886, II, xlv, 482.) 



If a rectangular glass vessel filled with water is penetrated at bot- 

 tom by a tube connected by means of a tap with a lateral reservoir, 

 containing water colored with aniline, and the whole is at the uniform 

 temperature of the room, there is produced, when the tap is opened, a 

 red jet in the middle of the colorless liquid. By modifying the orifice, 

 and by placing within the liquid articles of various forms against which 

 the liquid jet may impinge very varied plienomena are produced, which 



