7^2 Transactions of the American Institute. 



shaken. This powder, after being washed, first with hot water and 

 then with pure alcohol, consists of particles of copper, quite free of 

 any oxyd of the metal. Powdered copper may also be obtained by 

 subjecting the black oxyd of copper, when heated in a flask, to a 

 stream of coal gas, carried in and out by means of two tubes placed 

 in the cork. 



NEW METEOROLOGICAL INSTRUMENT. 



Prof. De la Rive, of Geneva, Switzerland, has invented an instru- 

 ment for determining the transparency of the atmosphere. It con- 

 sists of a double telescope with a single eye-piece, by which two 

 objects at known distances may be compared. Thus the effect of 

 the stratum of air between them may be noted. The inventor thinks 

 that a measure of transparency may be of great importance in a 

 sanitary point of view. He agrees with Pasteur, who supposes that 

 the light dry fog which sometimes intercepts the light is caused by 

 EQyriads of organic germs floating near the earth, which become 

 transparent when saturated with moisture, and are swept to the 

 earth b}^ heavy rains. Vaillant, however, believes that the haze 

 sometimes seen in fine weather is the effect of variations in the 

 density of the atmosphere, for reflected light, passing through 

 ftuch a medium, would not give a distinct impression of distant 

 ©bjects. 



NEW USE FOR TEAK OIL. 



The ravages of white ants in the wooden supports of the Indian 

 railways have been a very serious evil. Sleepers have been boiled 

 in poisonous solutions, and coated with coal tar, but such processes 

 were of no avail against the attack of these insects. When once 

 embedded in a sleeper, the vibrations to which it is subjected by 

 locomotives and cars passing over it, do not check the operations 

 of the ant. The Government of Madras has offered a reward for 

 a remedy. Mr. Brown seems to be the only one who has found a 

 preventive. It is the oil extracted from teak chips, which can be 

 obtained in any shipyard where this wood is used. They are 

 placed in an iron pot, having a hole in the bottom, which is set 

 upon another iron pot; both are placed in a hole in the ground, 

 and a brisk fire is made on the top. When the chips have become 

 chan-ed, a quantity of strongly scented oil will be found in the 

 lower pot, which makes a good varnish. Any timber varnished 

 with it will not be touched by white ants. 



