536 Wisconsin Academy of Sciences, Arts, and Letters. 
Fig. 2. The mud thermometer suspended from the tripod through 
a hole in the ice. The hammer appears just above the ice. The insulated 
cable leads to the thermophone box which is on the sled. 
In the first form of the thermometer (text fig. 1) the hammer 
was a simple cylindrical iron weight sliding on the smaller pipe. 
In this form the hammer is permanently attached to the ther¬ 
mometer and constitutes a source of some difficulty in handling it, 
especially when the thermometer is used in a launch. A heavy 
weight near one end, and that the upper end, when the instru¬ 
ment is put into place, increases the difficulty of handling it. 
When the thermometer is used through the ice, it is suspended 
from a tripod composed of three pieces of wood, 8 ft. long and 2 
in. by 4 in. These are connected at the top by a chain passed 
through a hole in each piece (text fig. 1 and 2). The launch from 
which the thermometer is used during the open season is also 
provided with a frame from which the thermometer can be sus¬ 
pended. The thermometer is suspended by a %-in. braided cot¬ 
ton rope. A twisted rope can not be used, since, when the ther¬ 
mometer is suspended from such a rope, it turns and winds up 
together the main rope, the wire cable leading to the galvanome¬ 
ter, and the two ropes which are used for working the hammer. 
With the braided cotton rope we have no trouble from this cause, 
though the instrument has been used in water as deep as 25 m. 
