VII. RECORDING INSTRUMENTS. 709 



The wind moves a system of hemispherical cups, like Eobinson's, (which 

 motion is replaced by clockwork for exhibition) acting on a circular plate, 

 whose velocity is ordinarily proportional to the velocity of the wind. Four 

 systems of sliding-rollers rest on this plate, whose bearings can be moved 

 round a vertical axis, the principal planes of which imitate all variations of a 

 wind vane. Each sliding roller can rotate about a horizontal axis, but only 

 in one direction, and after a half rotation an electrical contact is made. A 

 mechanism limits the contact to a fraction of a second. When the contact 

 is made, one of four wheels, with number-types, is moved. Every half an 

 hour the position of these four wheels is shown by printing numbers on a 

 strip of paper. The differences of those readings represent the mean velocity 

 of the wind from N., E., S., and W. They are converted into absolute values 

 by means of a table. Different mechanism adjusts the portion of every 

 sliding roller. 



2888. Complete Meteorograph. 



F. Van Rysselberghe, Ostend. 



4553. Drawings, on a large scale, of the Meteorograph of 



Padre Secchi, with printed description annexed. 



Observatory of the Collegia Romano, Rome ; Director, 

 Padre Secchi. 



AUTOMATIC REGISTERING APPARATUS. 



2889. Photographic Proofs, obtained at various depths and 

 at different seasons, to ascertain the penetration oi' the solar rays 

 in the waters of the Lake of Geneva. 



Prof. Dr. F. A. For el, Morges, Switzerland. 



From these observations it has been found that the extreme limit of pene- 

 tration at which the solar rays are capable of acting on chloride of silver is 



1. In the summer, when the water is, relatively speaking, not very clear, 



from 40 to 50 metres deep. 



2. In winter, when the water is less clear, 90 to 100 in depth. 



To enable a comparison to be made with the clearness of the water in other 

 lakes and in the ocean, and to give an idea of the degree of transparency of 

 the waters of Lake Leman, it should be mentioned that on the 10th March 

 1875, at noon, the sun being at 39 10', a white plate or plaque 25 centimetres 

 in diameter became invisible at a depth of 17 '0 metres. 



2890. Drawings of the principal parts of a meteorological 

 registering apparatus, viz. : 



a. Scale-barometer, natural size. 



b. Instrumental thermometer, natural size. 



c. Air thermometer, natural size. 



d. Clock-work and registering contrivances for only one of these 



instruments, since the mechanisms of all of them are iden- 

 tical ; natural size. Dr. P. Schreiber, Chemnitz. 



The apparatus represented in the drawings is intended for registering, at 

 intervals of 10 minutes, atmospheric pressure, atmospheric temperature, 

 and the temperature of the registering instruments. Only drawings could 

 be sent in, as the construction of the apparatus is not yet finished. The 



