274 Experiments made by the late Dr. Henry Draper 
gas was lighted at 9 o'clock, a. M., and at 11h. 20m. the 
temperature of the box was 67°5° F. The cross wires of a 
small telescope were then set on the less refrangible component 
of the sodium line. In 15 minutes the other component was on 
the cross wires, the spectrum having shifted the distance be- 
tween these sodium lines in this time. The displacement was 
toward the red, and the prism was rising in temperature. The 
then placed in the box. At 5b. 25m., P. M., this thermometer 
read 21°3° C. and the cross wires were set on the less refrangible 
sodium line. In 25 minutes the thermometer read 21°4° C. 
and the spectrum had moved over a little more than the dis- 
tance between the components. A second change of this 
amount required 41 minutes, the thermometer showing no 
change. Atih.2m., A.M. the spectrum had again shifted 
by a distance equal to that between the components of the 
sodium line, but had required 97 minutes to accomplish it, the 
thermometer reading 22°3° C. at the beginning and at the close 
of the experiment. The latter part of the time the spectrum 
shifted by only the width of one of the components in an hour. 
In a second experiment, an hour and six minutes was require! 
for this amount of displacement. The thermostat was then lelt 
in action over night. At 9h. 10m. the next morning the 
thermometer read 22° C. not having perceptibly changed since 
the last reading, while the sodium lines had shifted in seve” 
hours by only a little more than the distance between them. 
he gas was then turned off and the entire apparatus allowetl 
to remain at rest for several days, the temperature of the box, 
the position of the sodium lines, and their definition being 
observed by Mrs. Draper from time to time. The following 
are the values obtained: 
Date. Time, en hay ie» fs Definition. Displacement. 
Dec. 31st. 10pm. 68°F, 182°C. Excellent. 1:25 inches. 
Jan. Ist. 12 m. 69° F. 18°4° ©, ‘6 L166 = ° 
. 3pm. 68°F, 18°6° ©. “ 1083“ 
Jan. 2d. 10:45 a.m, 56° F, i? 0 Good. 2416 ° 
Jan. 4th. 12:30 pm. 50°F, 96°C Fair 3683 
ac t 
4:40 p.m. ‘ eG 
(Gas lighted in thermostat. 
‘ 7:30 p.m. 50° BF, 152°C. Entirely gone 2°083 
Jan. 5th. 10:25 a.m. 50° 
° 
BR Od 94° ©, Excellent. seo 
(Gas lighted in thermostat.) 
- 10:30 am 50° BF, 10'2° ©. Fair. ---- 
- 10:45 a.m. se 10°9° C. eee 
Bad. 
e 10:55 a.m. - 12; Entirely gone. ---- 
(Started the motor and in five minutes the definition was good. Put out the 
gas and a few minutes later stopped the motor. Definition lessened very slowly-) 
50° F. 112° C. Untirely gone. 
a ae 
