The Observatory at St. Martin. 361 



EXPLANATION OF EXTERNAL VIEW OF THE OBSERVATORY. 



A. Thermometer for solar radiation. 



B. Screen of Venetian blinds. 



C. Thermometer. 



D. Opening in ridge of the roof, closed with shutters, to allow use of 

 transit instrument. 



E. Rain guage with conducting pipe through the roof. 



F. Velocity shaft of the anemometer. 



G. Mast for elevating apparatus for collecting electricity. 

 H. Cord for hoisting the collecting apparatus. 



J. Copper wire for conducting the electricity into the building. 

 J. Direction shaft of the anemometer. 



EXPLANATION OF THE PLAN OF THE OBSERVATORY. 



A. Anemometer. 



B. Small transit for correcting time. 



C. Electrical machine for charging the Distinguisher. 



D. Peltier's electrometer. 



d. Space occupied by Drosometer, Polariscope, &c. 



E. Electrometer, e. Discharger. 



F. Distinguisher. 



f. Small stove — sometimes used in damp weather. 



G. Thermometer placed in the prismatic spectrum for investigations on 

 light. 



H. Nigretti & Zambra's barometers and cisterns, 118 feet above the 

 level of the sea. 



J. Small-tube barometer. 



J. Newman's barometer. 



K. Aneroid barometer. 



L. Quadrant and artificial horizon. 



M. Microscope and apparatus for ascertaining the forms of snow crystals. 



N. Thermometer, psychometer, &c, 4 feet high. A space is left be- 

 tween the two walls to insure insulation and prevent radiation. 



O. Ozonometer. 



P. Evaporator — removed in winter and replaced by scales for showing 

 the amount of evaporation from the surface of ice. 



Q. Post sunk in the ground, and 40 feet high, to carry the arms of 

 support for the Anemometer. 



R. Solar radiator. 



S. Venetian blinds. 



T. Iron rod beneath the surface of the ground connected with the 

 discharger to insure safety. 



