140 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



timate of the total resistance of a surface three hundred feet 

 long, such as the side of a ship, whether we assume such in- 

 crease to continue at the same rate throughout the last two 

 hundred and fifty feet of the surface, or to cease entirely af- 

 ter fifty feet. Froc. Brit. School of Adv. Sci., 1874. 



THE MOVEMENTS OF WAVES AND VESSELS AT SEA. 



The study of tlie motions of vessels is prosecuted in the 

 French navy with considerable diligence by means of the 

 apparatus invented by Madamet, and described in a note in 

 the 3IarUime and Coloiiial Heview, May, 1876. This appa- 

 ratus consists essentially of a Foucault regulator causing 

 two pencils to traverse a cylinder with perfect regularity ; 

 the whole apparatus being swung on gimbals in such a way 

 that every movement of the vessel is registered, as regards 

 direction, velocity, and time, on a sheet of paper. This appa- 

 ratus has been used on board of a number of French frigates, 

 such as i' Ocea?i, La Minerve^ and La Galissonniere, while ly- 

 ing in the port of Brest, in order to determine completely the 

 movements of vessels oscillating in a calm sea. At present 

 the apparatus is employed in connection with that devised 

 by Risbee, in order to measure the resistance of a vessel to 

 careening. Bevue 3IarUime et Coloiiiale, May, 1876, 481. 



VIBRATION OF FLUID COLUMNS. 



The fact that a column of air can be set into longitudi- 

 nal vibration has suggested to Kundt the possibility of pro- 

 ducing: similar lonsfitudinal vibrations in columns of water. 

 To this end he sets the tube containing the water in vibra- 

 tion, and finds that the success of his experiment dejDends 

 principally upon removing from the liquid all traces of gas, 

 whether the latter be absorbed or are in the shape of minute 

 bubbles. The gases absorbed by the liquid are partially 

 driven out by the vibrations, and appear as disturbing bub- 

 bles. The so-called tone figures of Kundt can be shown in 

 the vibrating columns of liquid as well as in those of air, 

 and can be used to determine the velocity of sound in the 

 liquid. It is found that the thickness of the glass tube has 

 an influence on the velocity of sound, such that the thicker 

 the tube the more rapid is the propagation of the sound 

 wave. 19 (7, VIII., 7. 



