THERMAL EFEECTS OE FLUIDS IN MOTION. 
330 
Series XXI. — Wooden Ball, 1 inch diameter. 
Velocity of air. ^ „ 
1’8 ... Equator 0‘045 warmer than Anterior Pole ... Posterior Pole 0‘052 warmer than Equator. 
2’7 ... Equator 0’056 warmer than Anterior Pole ... Posterior Pole 0'052 warmer than Equator. 
5'4i ... Equator 0’074 warmer than Anterior Pole ... Posterior Pole 0'035 warmer than Equator. 
10’8 ... Equator 0'052 warmer than Anterior Pole ... Posterior Pole 0’017 warmer than Equator. 
21'6 . . . Equator 0'037 warmer than Anterior Pole . . . Posterior Pole 0 008 colder than Equator. 
43'2 ... Equator 0" 011 warmer than Anterior Pole ... Posterior Pole 0 013 colder than Equator. 
54 ... Equator 0’019 colder than Anterior Pole Posterior Pole 0'014 colder than Equator. 
62 Posterior Pole 0'023 colder than Equator. 
83'8 Posterior Pole 0 041 colder than Equator. 
108 ... Equator O’OOl colder than Anterior Pole Posterior Pole 0'086 colder than Equator. 
Series XXII. — Wooden Ball, ^ inch diameter. 
Velocity of air. ^ 
1’8 ... Equator 0‘048 warmer than Anterior Pole ... Posterior Pole O'OoO warmer than Equator. 
5'4 ... Equator 0'030 warmer than Anterior Pole ... Posterior Pole 0'047 warmer than Equator. 
10'8 . . . Equator 0'023 warmer than Anterior Pole . . . Posterior Pole 0 031 warmer than Equator. 
21’6 ... Equator 0 008 warmer than Anterior Pole ... Posterior Pole 0'012 warmer than Equator. 
43‘2 ... Equator 0'006 colder than Anterior Pole Posterior Pole 0'009 warmer than Equator. 
54 ... Equator 0 019 colder than Anterior Pole Posterior Pole 0 006 colder than Equator. 
62 ... Equator 0‘026 colder than Anterior Pole Posterior Pole 0'014 colder than Equator. 
83'8 . . . Equator 0'040 colder than Anterior Pole Posterior Pole 0'031 colder than Equator. 
108 ... Equator 0'068 colder than Anterior Pole Posterior Pole 0 050 colder than Equator. 
The general result is that at slow velocities of air there is a gradual increase of tem- 
perature from the anterior to the posterior pole, but the reverse at high velocities. We 
observed a great effect for slow velocities at the commencement of an experiment, 
which gradually declined on continued blowing. This phenomenon was apparently 
owing to cu’cumstances in connexion with the temperature of the orifice and of the 
bellows. 
The causes of the thermal effects on the surface of balls slowly pass- 
ing through air are very complicated, as they arise from the effects of 
stopped air, fluid friction, and varied pressures. In order, if possible, 
to throw some light on these, we made the following observations : — 
1st. That when the 12-inch globe passed through the air at the velo- 
city of about 12 feet per second or under, the air at the equatorial part 
moved in the reverse direction. We did not observe the velocity, if it 
existed, at which this phenomenon ceased to take place 
2nd. An ivory ball, 1‘7 inch diameter, had holes drilled from points 
of the surface 90° asunder, which holes met at the centre of the ball. 
Into the lower one (see adjoining figure) a bent glass tube, partly filled 
with water, was cemented ; in the other, at c, a porous wooden plug 
was placed. It was then found that when c was made the anterior 
pole in a blast from the bellows, a pressure was experienced able to 
* See ‘ Proceedings of the Eoyal Society,’ June 18, 1857, p. 558. 
