Natural Philosophy, — Hydrodynamics. 367 
3. The Polar lights have no determinate connection with the 
earth. 
4. He never heard any noise proceed from them. 
5. Their common form, in Iceland, is the arched, and in a 
direction from NE. and W.SW. 
6. Their motions are various, but always within the limits of 
clouds containing them. 
HYDllODYNAMICS. 
12. Perhins''s Steam-Engine. — The delay which has taken 
place in the construction of Mr Perkins’s steam-engine, has arisen 
solely from the difficulty of constructing a generator capable of 
retaining the steam under high pressure, without leakage at the 
seams and joints. Under this difficulty, Mr Perkins most pro- 
perly declined to exhibit an imperfect experiment, which would 
have destroyed the character of his invention. AVe are glad, 
however, to find, that Mr James Eussell of Wednesbury, has 
succeeded in constructing a generator of wrought iron, without 
any seam or rivets, which we learn has been proved to resist 
the enormous and incredible pressure of twenty thousand pounds 
upon every inch of its surface. Mr Perkins considers this ex- 
traordinary piece of workmanship as enabling him to surmount 
all his practical difficulties. — See Newton’s Journal of the ArtSy 
vol. vii. p. 148. 
13. Mr Perhinis Steam-Guns. — The great power of Mr 
Perkins’s engine he has recently illustrated by some singular 
experiments. He has constructed a small apparatus, which, 
when connected with the generator, has been found to discharge 
ordinary musket-bullets at the rate of 240 in the minute, and 
with such tremendous force, that after passing through an inch 
deal, the ball, in striking against an iron-target, became flatten- 
ed on one side, and squeezed out. The original size of the bul- 
lets was 0*65 of an inch, but after striking the target, they were 
plano-convex, and their diameter 1.070 inches, and 0.29 of an 
inch thick. — Id. p. 107, 
II. CHEMISTRY. 
14. On the Nature of the Atmosphere In a curious 
paper on this subject, published by M. Vogel of Munich, in the 
B b 2 
