CHAPTER XXIII. 
EXPERIMENTAL PHILOSOPHY. 
THE works included in this department of our present volume are not numerous, 
nor of first-rate. importance; they bear, however, a considerable value, and we 
doubt not will be received by the public with complacence. Professor Aldini’s. 
volume on Galvanism exhibits a full detail of the wonderful effects produced by 
this newly-discovered agent on the nerves and muscles of animals, recently killed. 
Mr. Johnson’s laborious compilation of the scattered facts, illustrative of animal 
chemistry, merits great praise for its accuracy and minuteness, and will be acknow- 
ledged as a most useful body of facts and opinions by all those who are engaged 
in this interesting pursuit. Mr. Cavallo’s Experimental Philosophy is well calcu- 
lated to inspire young people with a desire of penetrating further into the majestic 
temple of Nature; and Mr. Accum’s System of Chemistry will be welcomed by 
the amateur, and may be gleaned with profit by the more experienced chemist. 
Dr. Black’s Lectures, which some years ago would have deserved the first rank 
among the popular systems of this science, from the delay in their public appear- 
ance, are likely to engage the attention of those principally who have enjoyed the 
pleasure and advantage of his personal instructions, and of those who are anxious 
to become acquainted with the style and manner of this eminent philosopher. 
Arr. I. he Elements of Natural and Experimental Philosophy. By 'Tiperivs 
Cavauo, F.R.S.  Lilustrated with Copper Plates. 4 vol. 8vo. 
THE phenomena of nature cannot 
fail of making an impression in various 
degrees on every mind: some will acqui- 
ésce in the idlest surmises, whilst others, 
by a comparison of various effects, will 
be enabled to class them together, and 
thus arrive to some general property to 
which these appearances may. be refer- 
ed. In making this classification it will 
appear, that number and extension are 
two qualities which enter into the con- 
sideration of most of these effects; and 
hence, without the study of the mathe- 
matics, the knowledge of the cause of 
effects in nature must remain very im- 
perfect. As many persons are unwilling 
to take the labour which is required to 
make the necessary progress in these 
studies, it becomes an object of some im- 
portance to devise means of rendering 
the science as popular as possible, and 
great praise is due to those who exert 
themselves inthis manner. At the same 
time all readers should be informed, that 
not Only their ideas must be very imper- 
fect, but that they in the end take more 
trouble in investigating any subject in 
the popular way, than they would do 
by examining it on its true principles. 
Thus in explaining the motion of the 
heavenly bodies, the great principles are, 
that a_body acted upon by two powers 
will describe the diagonal of a paral- 
lelogram, whose sides are the lines of 
directions of the powers; and that a 
body revolving round a center of force 
will describe equal areas in equal times 
about that centre. Now to him to 
whom parallelograms and triangles are 
familiar, the demonstration is simple 
and easy; to others the ideas must be 
weer confused, and it will be very difs 
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