106 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



been made by a proper committee : " The problem that Pro- 

 fessor Van Rysselbergh has endeavored to solve can be 

 stated in the following manner: It is desired to make an ap- 

 paratus, simple and inexpensive, in which a single graver 

 shall engrave npon a single cylinder the indications of a great 

 number of meteorological instruments of any nature whatever, 

 and these either close together or at a distance from the re- 

 corder. The author has resolved this problem by modifying, 

 in a very original manner, the apparatus originally described 

 by Wheatstone. A vertical cylinder controlled by a clock 

 makes, at equal intervals for instance, every ten minutes one 

 revolution around its axis ; a telegraphic circuit, of which 

 the instrument to be observed makes a part, is closed by the 

 movement of the cylinder; there is thus set at liberty a 

 graver which touches the surface of the cylinder, and marks 

 thereon perpendicularly to the generatrix a line whose length 

 is proportional to the indication of the instrument in question ; 

 at each revolution of the cylinder the graver descends a small 

 distance, so that w r e obtain a series of equidistant marks, the 

 extremities of which form the curve of the observation. The 

 cylinder is covered with a thin sheet of copper, smeared with 

 a little grease, and when this sheet has received the inscrip- 

 tions of the graver it is withdrawn and plunged into an acid, 

 so that it thus becomes an engraved plate, from w T hich one 

 can print copies at will. The plates that accompanied the 

 memoir of Professor Van Rysselbergh had been obtained by 

 this process, from which the simplicity and precision of the 

 instrument could be appreciated. The committee have re- 

 ported favorably upon the idea of Professor Van Rysselbergh, 

 and commended his invention to the approbation and encour- 

 agement of the Belgian government. Bull. Acad. Brussels, 

 1873,124. 



LOW WATER IN THE RIVER SEINE. 



Messrs. Belgrand and Lemoine predicted, four months in 

 advance, an approaching stage of very low water in the 

 River Seine, which would probably occur about the middle 

 of October. In making this prediction, they desired to say 

 that even though the summer months should be quite rainy, 

 yet would the flow of water not be sufficiently great to dis- 

 prove the truth of their prediction. It has been established, 



