456 Analyses of Books. [Junz, 
a good magnetic needle prepared for the purpose, the mean 
variation here has been found to be 241° west ; and from obser- 
vations made with the same needle in the early part of the year, 
there is reason to conclude that the variation westward has not 
attained its maximum, but that it is still increasing very slowly ; 
yet it has been mentioned in late publications in this country, as 
well as in Paris, that the magnetic needle is receding from its 
western limits. 
It is necessary to observe that no correct conclusion can be 
drawn from two or three cursory observations, however perfect 
the apparatus may be ;_ and that a regular series must be entered 
on to determine the question with any degree of accuracy. At 
the time of the equinoxes, the magnetic needle is often disturbed 
by strong electric winds ; and at the close of summer we have - 
observed that the needle generally indicates the greatest varia- 
tion: therefore, a month before and a month after the summer 
and winter solstices, seem the most proper times to commence a 
series of observations to determine the true mean state of the 
magnetic needle westward. 
ARTICLE VI. 
ANALYSES OF Books. 
Recherches sur VIdentité des Forces Chimiques et Electriques. 
Par M. H. C. G:rsted, Professeur a ? Université Royale de 
Copenhagne, et Membre de la Societé Royale des Sciences de la 
méme Ville, &c. Traduit de ? Allemand par M. Marcel de 
Serres, Ex-Inspecteur des Arts et Manufactures, et Professeur 
de la Faculté des Sciences a@ ? Université Imperiale; de la 
Societé Philomatique de Paris, &c. Paris, 1813. 
(Continued from p. 377.) 
From the statements given in the second.chapter of his work, 
of which an abstract will be found in the last namber of the 
Annals, M. CErsted draws the following conclusions : 
1. That the force of combustibility and the burning force are 
the ultimate chemical forces to which ourexperiments conduct us. 
2. That they are likewise the forces which give to bodies their 
physical properties. 
3. That we may consider these forces as the primitive and 
universal forces of bodies. 
Cuap. III.—Of the Action of Forces in the Chemical Circle. 
Our author gives the name of chemical circle to what is usually 
termed the galvanic or voltaic circle ; because he is of opinion 
that the phenomena of that circle are produced by the two 
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