1815.) Scientific Intelligence. 465° 
the pupil acquainted with a variety of important curves, and in- 
deed with the doctrine of curves in general. Lastly, let him pro- 
ceed to the inverse method. Let him accustom himself to. resolve 
as many problems as possible. 
We have no good elementary book on fluxions in English. The 
best is Thomas Simpson’s fluxions; but it is very inelegant, and 
he has been at no pains to smooth the difficulties. The best books 
in existence on fluxions are three of Euler, written in Latin, his 
introduction to the calculus of infinitely small quantities, and his 
works on the differential and integral calculus. I would be disposed 
to make use of them; but as the notation is different from our’s, 
that may be considered as an objection. Of the French ele- 
mentary books the best that I have seen is Bossut’s, Lacroix 
wants the art of arranging; hence his books are confused, and not 
very fit for students. 
III. Account of a Meteor. 
(To Dr. Thomson.) 
MY DEAR SIR, 
In the last number of your Annals of Philosophy, Mr. Luke 
Howard mentions a meteor, which was seen on the evening 
of the 29th of last month, and requests any person having ob- 
served the same to give him what information they can. I was 
walking out in the evening and saw the reflection of light on the 
ground, much like toa large flash of lightning; on looking up, 
the meteor was then passing with great velocity towards the north, 
and also declining: it then appeared to divide into a number of 
stars, much like a sky rocket when bursting. 
As your Annals generally embrace all foreign and scientific 
intelligence, 1 shall consider myself much obliged if through the 
Annals you would favour me with the description of a) Portable 
Machine for surveying land, invented by M. Pictet, an account of 
which I believe is published in the Archives des Decouvertes. 
I remain, dear Sir, yours truly, 
Oct, 23, 1815. ’ R. W. B. 
IV. Queries respecting Steam Engines and Steam. 
(To Dr. Thomson.) 
DEAR SIR, 
I observe by the Newspapers, that an important improvement 
has lately been made by employing rarified air in place of steam, 
as the moving power of engines; and the editor of the Monthly 
ine mentions that one of these engines is already at work, 
which requires only one twentieth of the fuel used by a steam 
engine of the like power. I am sure it would be very acceptable to 
your numerous meat wt if you would give a particular description 
of the machine, and the reason how so small a quantity of heat 
produces so great an effect. I have never seen any account of ‘the 
c heat of steam, of different degrees of elasticity: it is 
Vou. VI, N° VI. 2G . 
