8 
11. HAND-COLORED LANTERN SLIDE of the solar spectrum. Ex- 
hibited by C. C. Trowbridge. 
12. Set of LANTERN SLIDES illustrating some physical phenom- 
ena. Exhibited by C. C. Trowbridge. 
13. AIR PUMP with stopcocks automatically worked as valves. 
Exhibited by Prof. O. N. Rood. 
14. AIR PUMP with stopcock worked by hand asavalve. Ex- 
hibited by Prof. O. N. Rood. 
15. APPARATUS for measuring resistances up to ten million 
million ohms. Exhibited by H. C. Parker. 
16. APPARATUS for measuring resistances as lowas one millionth 
of anohm. Exhibited by H. C. Parker. 
17. APPARATUS for analysis of sound by resonance, used in inves- 
tigating the use of the mouth and nose cavities in articulating 
and singing; with photographs of voices. Exhibited by Dr. 
Floyd S. Muckey and Dr. W. Hallock. 
18. APPARATUS for comparing the rate of vibration of two tuning- 
forks by the photography of manometric flames; with nega- 
tives. Exhibited by Prof. W. Hallock. 
19. IMPROVED KEY for certain electrical work. Exhibited by H. 
Cushman. 
20. SEGER’S PYRAMIDS. Test pieces of different mixtures of feld- 
spar, clay, limestone, and quartz. Each of these test pieces 
has a different melting-point, thus forming a series which can 
be used in a furnace to record the temperature. 
21. SIEMENS’S WATER PYROMETER. A copper vessel protected 
by felt, and containing a definite amount of water whose initial 
temperature is recorded by a thermometer. Into this water is 
plunged a copper or platinum cylinder of given weight and of 
the same temperature as the furnace into which it was previ- 
ously placed. From the rise of temperature of the water, the 
temperature of the furnace is calculated. 
22. HOBSON’S PYROMETER consists of a copper tube with wooden 
handle at one side, having a thermometer at the outer end and 
