Notices respecting New Books. 57 



so exceedingly simple that no optical knowledge is required to 

 understand it. Dr. Priestley has reprinted Mr. Melville's expla- 

 nation, with the necessary diagram, in his History of Vision, 

 Light and Colours*, and we therefore refer the reader to either 

 of these works. 



When I received from my correspondent, then living on the 

 Continent, and whose name I do not feel myself at liberty to 

 mention, his account of the phantom silhouettes, I failed entirely 

 in producing them. I resumed the subject more than once with 

 the same want of success, and from this cause I believe I did not 

 take any notice of his communication. If he has published his 

 essay on the subject, I regret that I have not been able to find 

 it ; if he has not, and if this notice should meet his eye, I trust 

 he will enable me to mention his name, and give him the credit 

 of having first discovered the phamomena to which I have called 

 the attention of the reader. 



St. Leonard's College, St. Andrews, 

 December 2, 1S51. 



X. Notices respecting New Books. 



Elementary Physics ; an Introduction to the Study of Natural Philo- 

 sophy. By Robert Hunt, Professor of Mechanical Science in the 

 Government School of Mines, fyc. Reeve cind Benham. 1851. 



THIS book has been undertaken with the laudable intention of 

 placing clearly before the reader all the great deductions of phy- 

 sical science without the introduction of mathematics. Those who read 

 the preface and read the book, will be able to say whether the hope 

 held out by the former has been realized. Our own experiment in 

 this way is far from satisfactory. During the perusal of the work, 

 the total absence of scientific precision is constantly suggested ; very 

 little attention is paid to the definition of terms, and just as little to 

 the natural order of thought. A certain unscientific forgetfulness 

 is often evinced ; where, for example, the author speaks of " this 

 law," and when you inquire, " what law ?" you find him vanish- 

 ing in the haze of his own speculations. Thus at page 58 we read, 

 " by squaring the number of seconds, and multiplying the pro- 

 duct by 16| feet — a close approximation to the truth — we have the 

 height or the depth required." We can fancy the youthful reader, 

 longing for intellectual sustenance, demanding here, " what truth i" 

 Mr. Hunt does not inform him ; nay, he is worse than silent, for in 

 a foregoing page he has thrown him off the scent by assuming that 

 the distance through which a body is drawn by the force of gravity 

 in one second is 15 feet. A man may understand a subject, and 

 still be blessed with no faculty of expression ; and the book before 

 us demonstrates the converse of this proposition — that a clear under- 



* Vol. ii. p, 12b, fig. 163. 



