544 Wisconsin Academy of Sciences, Arts, and Letters. 
Fig. 4. Galvanometer of the pyrlimnometer. 
Fig. 5. Small receiver for electrical pyrlimnometer, about full size 
This receiver shows the form used in the first year, with flat glass cover 
for the thermal couples instead of the dome as shown in Plate XL, 
figure 5. This receiver was later used for measuring the absorption of 
radiation by snow and ice and by filtered water in a tank. 
The Galvanometer. The electrical currents set up by the sun 
in the thermal couples are measured by d’Arsonval galvanometer. 
This is of the marine type in which the suspended coil is attached 
to a wire under tension, so that it is less sensitive to the motion of 
the boat. As used at present, the galvanometer is kept on shore; 
but the type of construction makes it readily portable without get¬ 
ting out of adjustment. 
The appearance of this instrument is seen from text figure 4. 
Its base is 24 cm. long, 17.2 cm. wide at the front, and 8.5 cm. 
wide at the back; its height is 17 cm. The scale is in the front 
of the box and is 16 cm. long, divided into millimeters. The figure 
shows the windows by which the scale is illuminated. 
The galvanometer is provided with a shunt coil, and when this 
is included in the circuit the swing of the galvanometer is about 
one half as great as when the shunt is cut out. It is therefore 
possible to use the galvanometer for determining the full intensity 
of the sun. A rate of 1 cal. cm. 2 min. would cause a deflection 
