590 SEC. 14. METEOROLOGY. 



of the aneroid indicates the pressure of the air at the time of observation. 

 Having already described the construction of the aneroid, it is only necessary 

 to explain the method by which it is made self-registering. Connected with 

 the lever that carries the chain round the arbour is a long watch chain that 

 passes through the top of the aneroid over a pulley ; it terminates with a 

 metallic point, which is kept in working position by means of a vertical bar ; 

 this is capable of revolving upon its points. Behind the metallic point or 

 pencil is the vertical revolving cylinder covered with the metallic paper ; this 

 is moved by the clock, which also presses the pencil point down upon the 

 paper, and leaves a mark at each hour. 



2887. A Von Getting en's " Self-recording Wind Com- 

 ponents Integrator." Constructed by P. Schultze. 



Dr. Arthur Von Oettingen, Professor at the Imperial 

 University, Dorpat (Russia). 



The wind moves a system of hemispherical cups, like Robinson'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. A Complete Meteorograph. 



F. Van Rysselberghe, Ostend, 



AUTOMATIC REGISTERING APPARATUS. 



2889. Photographic Proofs, obtained at various depths and 

 at different seasons, to ascertain the penetration of the solar rays 

 in the waters of the Lake of Geneva. 



Professor Dr. F. A. Foret, 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 more liquid, 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. 



