THEEMAL EFFECTS OF FLUIDS IN MOTION. 
329 
Series VIII. 
Position of junction. 
Velocities in the 
alternate experiments, 
in feet per second. 
Difference 
of thermal 
effect. 
Estimated 
effect of low 
velocity. 
Thermal 
effect of high 
velocity. 
Velocity due 
to 1 °C. 
Mean. 
Flat side against 
the air ] 
Thin edge against ' 
the air 
' 
> 
85*8 and 40 
156‘5 and 52 
164'4 and 48 
182-4 and 54-3 
0-165 
0-683 
0-736 
0-811 
0-046 
0-085 
0-074 
0-074 
d-211 
0-768 
0-810 
0-885 
186-6 
178-61 
182-6 1 
193-9 
180-6 
1 
The general mean of all the foregoing results is I79T5 feet per 1° Cent. The 
phenomena hitherto observed seemed to point to the effect of stopping air as a cause, 
since 145 feet per second is the velocity of air equivalent to the quantity of heat 
required to raise its substance, under constant pressure, by 1° Cent, temperature ; and 
it was reasonable to infer that a portion of the effect was lost by radiation. The follow- 
ing experiments, made with a junction of fine wires covered loosely with cotton-wool 
or tow, enabled us to eliminate all effects but those due to stopped air. Their results 
will be found to agree closely with theory. 
Series IX. 
Velocities in the 
Difference 
Estimated 
Thermal 
Velocity due 
to 1 ° C. 
Position of junction. 
alternate experiments, 
of thermal 
effect of low 
effect of Iiigh 
Mean. 
in feet per second. 
effect. 
velocity. 
velocity. 
91-3 and 34 
0-25 
d-04 
0-29 
169-6 
Cotton-wool closely 
112 and 26 
0-447 
0-025 
0-472 
162-8 
1 
tied about the junction<^ 
135-8 and 40-6 
1-37 
0-14 
1-51 
110-5 
>.148-76 
of fine wires 
1 40-3 and 24 
0-823 
0-024 
0- 847 
1- 273 
152-4 
167-6 and 43-5 
1-188 
0 085 
148-5 
J 
94-1 and 35 
0-494 
0-079 
0-573 
124 
Junction of fine wires 
95-7 and 25-3 
0-426 
0-032 
0-458 
141-1 
I 
placed in a small wicker 
basket filled with cotton-"^ 
105-5 and 27*6 
113-5 and 33 
0-33 
0-409 
0-026 
0-038 
0-356 
0-447 
168- 3 
169- 5 
>■144-53 
wool or tow 
116-8 and 33 
0-639 
0-055 
0-694 
140-1 
116-8 and 47-4 
0-739 
0-145 
0-884 
124-2 
When the junction was placed in the basket, without any cotton-wool or tow, a 
velocity of I GOT ft. per second was required to give 1°. N.B. The basket was so open 
that its orifices amounted to half the entire area. 
In several of our experiments with very slow velocities there appeared to be a greater 
evolution of heat than could be due to the stopping of air. This circumstance induced 
us to try various modifications of the surface of the whuled body. In the first instance 
we covered the bulb of the thermometer used in the second series of experiments with 
five folds of wi'iting-paper, and then obtained the following results : — 
