262 Clironicles of Science. [April, 



its preparation: the best is probably that of MM. Miiller and 

 Paul. Their process consists in passing a current of dry and pure 

 chlorine gas into pure and absolute alcohol, until the contents of the 

 flask are, after about seventy hours, converted into a white and 

 crystalline mass ; when this operation is properly conducted, a large 

 quantity of hydrate of chloral is obtained. Hydrate of chloral is 

 readily sublimed, and may be thus obtained as a dry, snow-white, 

 neutral crystalline powder. It does not exhibit any smell at the 

 ordinary temperature of the air; it volatilizes slowly, without 

 absorbing much moisture, unless it be placed in a very damp place ; 

 it fuses at 56°, boils at 145°, is completely soluble in a small quan- 

 tity of water, and also soluble in alcohol, ether, chloroform, sulphide 

 of carbon, benzol, and fatty substances. Its aqueous solution ought 

 to be neutral to test-paper, and should not become turbid by a solution 

 of nitrate of silver. 



It is now proposed to make the reflecting surfaces of looking- 

 glasses of platinum instead of tin amalgam or silver. M. Jouglet 

 prepares the platinizing compound in the following manner : — Yery 

 thin platinum foil is dissolved in aqua regia, the solution carefully 

 evaporated to dryness, the solid chloride next placed on a triturating 

 marble, and gradually mixed with essential oil of lavender. When 

 incorporated with the chloride, the mixture is placed in a porce- 

 lain capsule, and left standing for several days : the fluid is decanted 

 from any sediment, and filtered. As flux for 100 grains of platinum 

 the following ingredients are used : — 25 grains of litharge and 

 25 grains of borate of lead, mixed and triturated together with 

 about 10 grains of essence of lavender; this is next mixed with the 

 platinizing fluid. After a layer of platinum has been formed upon 

 the glass, it is fixed by burning it in by placing the glass in pecu- 

 liarly-constructed muffles. 



From a series of observations made at Monaco, on the shores of 

 the Mediterranean, Dr. Gillebert d'Hercourt concludes that there is 

 always on the sea- shore an atmosphere impregnated with saline 

 particles ; this layer of air has, at the above-named place, some 500 

 metres horizontal and 60 metres vertical extent. This impregna- 

 tion of salt is due to what the author terms " pulverization " of the 

 sea-water by the breaking up of the surf, and is not directly in- 

 fluenced either by barometric pressure, hygrometric state of the 

 atmosphere, or temperature. This hydro-mineral dust, as it is 

 called by the author, is, unless there happen to exist near the coast 

 physical obstacles in the shape of high mountains, carried far away 

 inland, and is not to be confounded with what is of more coarse 

 nature, and termed "spray," which is only quite local and produced 

 when a gale of wind blows. The author states that, even on calm 

 days in winter, the atmosphere near Monaco is up to a height of 70 



