34-1 Analysis of Scientific Books. 



Fourier and Oersted have extended these researches, and de- 

 veloped a series of very interesting phenomena, connected with the 

 generation of electricity in metallic bars by change of temper- 

 ature. These circuits they call thermo-electric, in opposition to 

 the common galvanic arrangements which they properly enough 

 term hydro-electric. Some details of the experiments will be 

 found in a former Number, under the head of Foreign Science* . 



Chapter 6th. On the electro-negative bodies, oxygen, chlorine, 

 iodine, aud fluorine, is clearly and candidly drawn up. The next, 

 great division contains the electro-positive bodies, subdivided into 

 groups, each of which occupies a chapter. 



Chapter 7th is entitled, " Of simple acidifiable bodies, (not 

 metallic,) and their combinations with oxygen, chlorine, iodine, and 

 fluorine." Here we have the usual six bodies, hydrogen, nitrogen, 

 charcoal, boron, phosphorus, and sulphur, to which he has added se- 

 lenium. We cannotapprove of the single term acidifiable applied to 

 characterize the above bodies. Nitrogen and hydrogen may as pro- 

 perly be styled alcalifiable bases, as acidifiable ; for they form ammo- 

 nia. And when hydrogen combines with chlorine, we may regard the 

 chlorine as the acidifiable base, as well as the hydrogen. Dr. Henry 

 should have contented himself with the title electro-positive bo- 

 dies (non-metallic,) which involves no hypothesis, and to which no 

 objections can be urged. The metals, on account of their num- 

 ber, may indeed, be conveniently subdivided into such as afford 

 alkalis, earths, oxides, and acids. The details of this chapter 

 merit equal praise to that which we have bestowed on the pre- 

 ceding. Under the compound of hydrogen and nitrogen (ammo- 

 nia) he has introduced the salts formed with this alkali, and the 

 acids he had previously described. The reasons which he assigns 

 for this insulation of the ammoniacal salts among the non-me- 

 tallic electro-positives, and their compounds, do not appear to us 

 satisfactory. 



Chapter 9th contains the metals with their oxides, chlorides, 

 iodides, and the combinations of the oxides with the previously 

 described acids, or the salts. His details appear to be correct, 

 and as minute as the size of his work would admit. 



It is in the general discussions or philosophy of chemistry that 

 Dr. Henry seems to be least at home. Thus in the introductory sec- 

 tion on the general properties of metals, wc find him retailing as 

 important special laws, propositions which have been long ago 

 merged into the. great system of chemical equivalents, of which 

 they constitute particular corollaries. Indeed one of the general 

 principles advanced by Dr. Henry, is manifestly no general prin- 

 ciple at all, as we shall presently see. 



That the quantity of acid which different metals require for 

 saturation is in direct proportion to the quantity of oxygen in their 

 * Vol. xv. p,l26> 



