464 Scientific Intelligence, [Dee . 
visible. with respect to the determinate force er strength that is in 
matter. The primitive figure of the common salt isa little cube; 
of. vitriol, a rhomboidal parallelopipedon ; of nitre, a prism whose 
basis is an equilateral triangle ; and of alum, a quadrangular pyra- 
mid. From these figures proceed those which they constantly affect 
in their erystallizations, provided that they are kept as free as pos- 
sible from all foreign mixtures.” This looks like an anticipation of 
Haiiy’s doctrine of the primitive molecules of bodies. Whether it 
be so or not, can only be determined by a perusal of the book itself, 
which I have never had an opportunity of seeing. a 
Il. Fluxions. 
Want of room prevented me in the last number from making , 
some observations in answer to the queries respecting fluxionsy, 
proposed in p. 394 of the present volume. When Professor 
Christison says that fluxions might he easily understood by a person 
who has only made himself acquainted with the first two books of 
Euclid, I presume he is far from recommending sucha plan to be 
actually followed. He merely makes use of the expression to make 
the reader sensible that fluxions contain nothing mysterious, and 
that they are easily comprehended. ‘To study fluxions with so 
little mathematical knowledge would be useless, because the pupil 
could not in that early stage of his progress apply them to any 
useful purpose. The mode of studying mathematics, which ap- 
pears the simplest and easiest, is to learn the first four books of 
Euclid; then to make the pupil acquainted thoroughly with vulgar 
and decimal fractions, and with algebra as far as the solution of 
quadratic equations. With this knowledge the fifth book of Euclid 
or the doctrine of ratios, which is so important in mathematics, is 
easily comprehended by the pupil. A very perspicuous demonstra- 
tion of the principal theorems in it will be found in Saunderson’s. 
Algebra. The pupil may then study the sixth book of Euclid, ‘and 
make himself master of the 11th and 12th. I consider Mr. Play~ 
fair’s substitution of a variety of demonstrations from Archimedes 
as an improvement of the 12th book. Heé may them return . back 
to Algebra, learn the method of resolving cubic and biquadratic 
equations,,the nature of equations in general, and the various 
modes of solving them by approximation. ‘The properties of figu- 
rate numbers, of logarithms, and the doctrine of. series may also 
be learned. »‘The pupil then goes to trigonometry, and makes hitn- - 
self acquainted with plain and spherical, with the arithmetic of 
sines and tangents, and with the practical method of measuring 
heights and distances. He may then go to conic sections, and 
make himself acquainted with the properties’ of the parabola, 
ellipse, and hyperbola. After this fluxions come with propriety. 
"Lhe direct method occasions no difficulty whatever, and will yield 
much pleasure from the facility with which it enables the pupil: to 
draw tangents to curves, to solve the questions respecting maxima 
andminima,-&c, Here an opportunity may be taken of making. 
- ax 
