Theory of the Pneumatic Parador. 301 
as the author of a new theory of storms, and one by Mr. Asa 
Spencer. Another explanation, different in some respects from 
either of the preceding, is contained in the number of the London 
Mechanics’ Magazine for June, 1839. 
Professor Espy’s solution of thé phenomenon, is in some re- 
spects similar to Mr. Abbot’s, though, we if may judge from the 
date of its publication, posterior in point of time. Being sup- 
ported, however, exclusively by theoretical reasonings, it has left 
the question still open to dispute, and the contradictory opinions, 
which from time to time have since been advanced on the sub- 
ject, would seem to show, that an attempt to detect their errors, — 
and to establish the true theory, on the basis of direct, unequivo- 
cal experiment, would not be a work of supererogation. 
Prof. Hare, whose explanation is similar, as it respects its lead- 
ing principle, to that of Dr. Page, attributes the phenomenon to 
the afflux of air against the disks, occasioned by the radiating 
currents carrying with them, as they issue from between the 
disks, some of the contiguous air. He demonstrates by a very 
ingenious process of reasoning, that the velocity with which the 
two disks tend, from the force of the blast, to move asunder, is as 
many times less than the velocity of the blast, as the area of the 
movable disk is greater than the area of the orifice of the tube. 
Thus if the diameter of the disk and that of the orifice be as eight 
to one, the area of the former must be sixty four times greater 
than that of the latter, and consequently, in this case, the disks 
have no tendency to move asunder with a velocity greater than 
one sixty fourth of that of the blast. Hence he infers, that the 
blast tends to corr icate only a very small velocity, and inclines 
with a very small force to separate the disks. It has been shown 
that the afflux of air against the movable disk,.though as the ex- 
periment is usually performed auxiliary, is not essential to the 
adhesion of the disks. It is however adequate to sustain the mere 
weight of a second disk of letter paper, and of the same size of the 
first, as may be thus shown. Through the centre of the movable 
disk, to prevent it from sliding out of place, let a small needle pass 
and project on each side. Having made a small hole through the 
disk of letter paper, so that it move freely on the needle, place it 
underneath the movable disk, and both underneath the fixed one. 
On blowing through the tube, the disk of letter paper, being pro- 
Vol. xxxix, No. 2.—J uly-September, 1840. 39 
