294 On the received Theory of Heat. 
which the electric sparks are dimly seen. The stars of the fourth 
magnitude are made by spaces formed in the same manner, but 
covered with a thicker piece of paper. Thus I was enabled to 
give to each star its proper degree of brightness ; and. by these 
means I conceive a more exact representation of the celestial 
bodies can be given, than by any other method as yet known. 
In this scheme are represented upwards of sixty stars, besides 
the two great nebule which appear in the southern part of the 
heavens. To imitate the latter, I cut two holes in the paper, 
in the form of the nebule.—Here I passed the train of tin-foil 
through the paper, and at the back of the scheme carried it 
round the edges of these holes, leaving a few intervals for sparks. 
At the back of each hole I fixed a piece of Bristol board consi- 
derably larger than the aperture, and bent so that the part op- 
posite the hole should be about half an inch behind the level of 
the scheme. The paper thus fixed served as a screen to receive 
the light of the sparks given at the back round the holes ; and 
being by that means illuminated, while the general face of the 
scheme was in darkness, filled up the aperture as it were with a 
nebulous whiteness, giving as I apprehend a tolerably just image 
of the original. 
In damp weather these figures, like almost all electrical appa- 
ratus, require to be dried before a fire previously to their being 
used. 
The advantages which are derived from the use of paper in- 
stead of glass must be obvious. It is much less expensive. By 
joining together a number of sheets it can be made of any size ; 
and as it will not break, it is much more portable; which last 
circumstance must recommend it strongly to such as have fre- 
quent occasion to remove their apparatus from one place to an- 
other. I am, sir, 
Your obedient servant, 
Hill-top School, Birmingham, Row.anp Hitt. 
Oct. 12, 1818. 
XLVII. On the received Theory of Heat. By A CorreE- 
SPONDENT. 
To Mr. Tilloch. 
Sir, — Perr me to lay before your readers my reasons for 
objecting to the received theory of heat. I am strongly inclined 
to believe there is no such thing—any more than that there is an 
elementary principle of sound. 
Chemists and philosophers agree that. the particles of heat 
are infinitely smaller than any other particles—that insinuating 
themselves 
