58 Xutices respecting New Books. 



standing is by no means the invariable accompaniment of the pen of 

 a ready writer. 



Mr. Hunt informs us that " if we cut a cone perpendicularly to 

 the base, the section is a triangle." It is so in one case only, and 

 there are a million other cases where the section is not a triangle. 

 The definitions are obscure ; take, for instance, the following : — 

 " The centre of gravity is nothing more than the central point of 

 parallel or equal forces." In page 72 reference is made to the lean- 

 ing towers of Pisa and Bologna ; what the lines cd and ab, referred 

 to by Mr. Hunt, have to do with the matter we are at a loss to con- 

 ceive ; they are not the lines of direction, for neither of them passes 

 through the centre of gravity. In page 85 Mr. Hunt speaks " of the 

 centre of gravity being no longer at right angles to the plane ;" and 

 in page 86 he says, " The gravity of the body is decomposed into 

 two forces, one drawing it to the earth, acting at right angles to the 

 plane, and causing the pressure, the other acting parallel to the in- 

 clined plane and forcing the weight down it !" It would be useless 

 to comment on the infraction of the first principles of mechanics and 

 of common sense involved in these quotations. Mr. Hunt's defini- 

 tion of centrifugal force is incorrect, being the definition of quite 

 another force ; and when, in connexion with this subject, he speaks 

 of " an impulsive force exactly balanced against a statical power, a 

 system of harmony being the result," we confess our inability to 

 understand him. 



In page 121 it is stated, " that fluids issuing from orifices have a 

 velocity proportional to the height of the surface of the fluid above 

 the orifice." This is incorrect ; the velocities are proportional to the 

 square roots of the heights. The example in page 69 is wrong. 

 Did Mr. Hunt practically test Bunsen's cells before he condemned 

 them ? An experience of many years enables us to state that our 

 author's animadversions on this admirable invention are wholly 

 groundless. If the zinc collars are attacked as stated, it is the 

 fault of the experimenter, not of the battery. For the sake of 

 those who possess cells of Bunsen's construction we may remark, 

 that the chief point to be secured is a good metallic contact between 

 the coal cylinder and its encompassing ring ; the interior of the 

 latter must be rendered clean and bright by the application of a little 

 sand and dilute hydrochloric acid. 



In page 293 we are informed, that " if we hang at the end of a 

 magnet a weight which is nearly as much as it will support, and 

 then bring another magnet near to the end to which the weight is 

 attached, it will fall off." This is true if the poles are of opposite 

 qualities, but false if the poles are similar ; in the latter case the 

 weight will cling with increased intensity. In page 336 our author 

 writes : — " We speak of free caloric, and mean thereby the circum- 

 stance of heat becoming sensible, as when diffusing itself in its ten- 

 dency towards an equilibrium through all surrounding bodies. When 

 an equilibrium is restored, and all neighbouring bodies are at an 

 equal temperature, the agency is said to be latent, or in a state of 

 repose." The evident security with which this extraordinary annota- 



