342 Analysis of Scientific Books. 



recommend him to erase the second section, and to enlarge and 

 extend the third, illustrating it by a few wood-cuts of the appara- 

 tus there referred to. The fourth section entitled " Theory of the 

 changes produced by (galvanic) electricity ;" and the fifth, on the 

 theory of the action of the galvanic pile, touch upon some very in- 

 tricate and abstruse parts of chemical reasoning, but upon which 

 no very satisfactory or luminous conclusions have as yet been ar- 

 rived at. We are generally led to regard bodies as endowed with 

 certain inherent or natural electrical states, which render them 

 either attractive of each other, or of surfaces oppositely electrified ; 

 we consider these opposite electricities as partially or entirely an- 

 nihilated by combination, and to this source we may refer that re- 

 markable extrication of heat and light, which so commonly an- 

 nounces intense chemical action. We may account for the des- 

 truction of common chemical attraction between two bodies, by 

 supposing one of them to have an electrical state opposite to its 

 natural one conferred upon it ; while by exalting the natural elec- 

 trical energies, we may explain their increased tendency to union. 

 But all these assumptions are purely hypothetical, and still more 

 so are those which our author has adduced in reference to the ac- 

 tion of the pile, that is, to the source of its electricity. When we 

 know what electricity is, we may presume to talk upon these mat- 

 ters, but at present we must rest content with a knowledge of 

 facts and effects, and our stock must be infinitely and diligently 

 multiplied before we can presume to determine upon the source of 

 electricity, either in the common machine, or in the pile of Volta. 



The sixth section gives a succinct and tolerably correct account 

 of the most important electro-magnetic phenomena, in which, how- 

 ever, hypothesis and facts are rather too indiscriminately blended ; 

 and although we have great respect for Messrs. Arago and Ampere, 

 we think they have indulged in electro-magnetic speculations, which 

 border upon absurdity. Our information upon this very curious sub- 

 ject is extremely limited, and we do not hesitate to ascribe to the 

 researches of Oersted, Davy, Wollaston, Faraday, and Siebeck, all 

 that has really and actually been acquired in respect to it. The 

 grand and important fact that a metallic wire, through which a 

 current of electricity is passing, affects a magnetic needle, we owe 

 to M. Oersted. Let us imagine a wire of platinum placed in the 

 magnetic meridian, and a delicately-suspended magnetic needle 

 underneath, near md parallel to it; in this state of things nothing 

 particular will happen either to the wire or the needle : let us now 

 connect the extremities of the wire with a voltaic battery, the 

 right-hand extremity being in contact with the last zinc plate and 

 the left-hand end with the last copper-plate, so that in the hypo- 

 thetical language of electricians, a current of electricity may tra- 

 verse the wire from the right to the left. Under these circum- 

 stances the magnetic needle will no longer remain pointing N. and 



