Intelligence and Miscellaneous Articles. 77 



An instrument in actual use having an opening of 8 millim. 

 deflects its galvanometer 30 divisions of its scale when the hand is 

 held a foot from the opening. A lighted match at six feet drives 

 the needle around to its top. — Silliman's American Journal, 

 December 1887. 



APPARATUS FOR ILLUSTRATING THE FALL OF BODIES IN A 

 VACUUM. BY J. PULUJ. 



This apparatus has the advantage over others that it demonstrates 

 the property that all bodies fall at the same rate in vacuo in a very- 

 simple manner and always with certainty. It consists of a glass 

 tube 4 centim. wide, and 150 centim. in length, closed at both 

 ends, having been previously exhausted ; in it are contained the 

 bodies, an iron bullet 1*5 centim. in diameter, and a light feather, in 

 the quill-end of which is a fine iron needle-point 2 millim. in 

 length. At the bottom of the vertical tube a caoutchouc stopper is 

 inserted to protect the glass tube from breakage by the falling 

 bullet ; and at the top a brass flanged tubulure is cemented, in 

 which an electromagnet with an iron core can be screwed. The 

 tube is suspended vertically in the fork of a wooden support, by 

 means of two pegs affixed to the electromagnet. For exciting the 

 electromagnet a powerful battery of about 3 Bunsen's elements, or 

 an accumulator consisting of three coils, is used. 



To make the experiment, the tube is gently inclined until the 

 feather and the ball are in the field of the electromagnet, the 

 electrical current is closed, and the tube placed on the support. 

 Both the feather and the ball are held at the top of the glass tube, 

 and fall simultaneously the moment the current is opened. — 

 Berichte cler Kaiserlich. Alcacl. in Wien, Nov. 3, 1887. 



ATTEMPT TO APPLY THE DIFFUSION OF GASES AND VAPOURS 

 THROUGH POROUS BODIES TO DETERMINING THE AMOUNT OF 

 MOISTURE AND CARBONIC ACID IN THE SURROUNDING AIR. 

 BY F. SCHIDLO WSKY. 



The author has repeated the experiments of Dufour on the 

 diffusion of air and aqueous vapour, and has come to the conclusion 

 that in this phenomenon the absorption of vapour by porous bodies 

 plays an important part. 



If, for instance, we take a closed porous cylinder which contains 

 dry air under ordinary atmospheric pressure, and in connexion 

 with a water-manometer, and we place it in another cylinder in 

 which the air is always saturated with aqueous vapour by the 

 presence of water, then, according to Dufour, the manometer at 

 once shows a decrease of pressure of about 10 to 12 millim., which 

 afterwards becomes equalized. 



Conversely, when the same cylinder is filled with moist air, and 

 brought inside a dry cylinder, there is an increase of about 20 

 millim., which also is afterwards equalized. 



These phenomena are thus explained by the author : — 



