8 
30. Four of ten MAXIMUM RECORDING THERMOMETERS, 
sealed in glass tubes to protect them from the pressure of 
the overlying water. Used in the deep well at Wheeling, 
W. Va. 
31. SECTION showing the geological formations passed through 
by the deep well at Wheeling, W. Va. 
32. CURVES showing the rise in temperature in the deep well at 
Wheeling, W. Va. Observations of 1891. No water in the 
well. 
33. CURVES showing the rise in temperature in the deep well at 
Wheeling, W. Va. Observations of 1893. The well was full 
of water, and owing to a slight ‘“‘cave-in” at about 3300 feet, 
it was impossible to get the thermometers down to the bottom 
of the well. 
34. PLAN OF COAL-MINE, “Riverside No. 1,” in which tem- 
peratures were observed during the summer of 1891, to 
obtain a reliable value for the ‘‘surface” temperature, at 
Wheeling, W. Va. 
Nos. 29-34 exhibited by Prof. Wm. Hallock. 
DEPARTMENT OF (PEER @GRICIEY. 
In charge of Prof. M. I. Pupin. 
35. ELEVEN THOUSAND VOLT DIRECT CURRENT DYNAMO. 
Designed and exhibited by Prof. F. B. Crocker. 
36. APPARATUS FOR MEASURING SELF-INDUCTION in terms 
of the new unit, ‘‘the Henry,” the name of which unit was 
first proposed by Professors F. B. Crocker and M. I. Pupin, and 
officially adopted by the Electrical Congress in Chicago. Ex- 
hibited by the Electrical Department of Columbia College. 
37. Motor DyNAmos, for transforming direct currents into 
direct or alternating currents of lower or higher potential. 
Especially useful in laboratory work. Exhibited by Prof. F. 
By Crocker. 
