Scierityic jReviems. 419 



On the whole, this first part of the Society's Transactions is 

 highly creditable to so young an institution. The work will be in- 

 dispensable to the student of the natural history of Great Britain ; 

 ana we strongly recommend.it to the patronage of our readers. 

 Any little faults which the critic may detect in these first fruits, 

 should meet with an indulgent eye; for we are convinced that, 

 coming from such good husbandmen, they give promise of a noble 

 harvest. 



Elements of the Economy of Nature. By J. G. M'Vicab, A.M. 



OuK review of this work, in the Number for July last, will be 

 fresh in the recollection of our readers. We have received a long 

 letter from Mr. M 'Vicar on the subject, from which it is only do- 

 ing the author justice to extract the following: — 



" You mention that I am wrong as to two matters of fact with which you hap- 

 pened to meet. I doubt not but there are many ; nevertheless, you will find 

 that I am right in the two cases brought against me. With regard to the atomic 

 structure of ammonium I am astonished, if it be the same gentleman who has re- 

 viewed me on atomic chemistry, and has pointed out tliis circumstance ; for that 

 which he says I affirm with regard to the structure of ammonium is identical 

 Vith that winch he says is the general belief. Azote having in my work the same 

 atomic weight as Dalton assigns it, that is, half that which the reviewer has in his, 

 eye ; one atom of azote and two of hydrogen, according to my views, give the 

 very same composition as one of azote and four of hydrogen according to the other 

 view. With regard to the specific gravity and volume of iron, the facts alleged 

 in my work I learned at iron-foundries, when I was studying the phenomena of 

 this curious substance. I may mention, with regard to its volume, that it is an 

 yniversal practice to make the mould, into which liquid cast-iron is poured, l-8th 

 of an inch per linear foot larger than the metal is required when fit for use ; be- 

 cause it is found that average cast-iron contracts from the liquid state to that fit 

 for use by this amount." 



In reply to the astonishment of Mr. M' Vicar, we quote the three 

 lines which led us astray. Speaking of ammonia, he says, — 



" When under the metalliferous induction of the mercury, and 

 of what may be regarded as the metalliferous pole of the voltaic 

 axis, those particles of hydrogen which are not attached to the axis, 

 ^re given off, and a form, which is that of arsenic, without its two 

 terminal particles of hydrogen, remains." — Elements, p. 309. 



We took these worrfs as they stand, and understood them in their 

 common acceptation, which, without reference to the atomic weight 

 of azote, which has nothing to do with the matter, is simply that to 

 form ammonium, 9.mmoi\vd gives o/f" hydrogen. We are happy, how- 

 ever, to find that M. M'V. does not mean to advance such a state- 

 ment, and consequently that his words are to be interpreted ac- 

 cording to his views of ultimate atoms. 



In the case of cast-iron Mr. IM'V. is right as to the practice of 

 foundries, and still he is wrong in his book. He has a most per- 

 verse way of drawing conclusions, being determined to see spme- 



