306 Notices respecting New Books. 



passes through or beyond P has only two points of minimum 

 and one of maximum velocity of gliding. Hence the latter class 

 of lines cause less commotion in the water than the former. 



14. On the water-line P Q which traverses the point P itself, 

 the velocity of gliding changes more gradually than on any 

 other water-line having the same proportion of length to breadth. 

 Water-lines possessing this character can be constructed with 

 any proportion of length to breadth, from ^/3 (which gives an 

 oval through L and P) to infinity. The liner of those lines are 

 found to be nearly approximated to by wave-lines ; but are less 

 hollow at the bow than wave-lines are. 



15. The author shows how horizontal water-lines at the bow, 

 drawn according to this system, may be combined with vertical 

 plane lines of motion for the water at the stern, if desired by the 

 naval architect. 



16. In this, as in every system of water-lines, a certain rela- 

 tion (according to a principle first pointed out by Mr. Scott 

 Russell) must be preserved between the form and dimensions of 

 the bow and the maximum speed of the ship, in order that the 

 appreciable resistance may be wholly frictional and proportional 

 to the square of the velocity (as the experimental researches of 

 Mr. J. R. Napier and the author have shown it to be in well- 

 formed ships), and may not be augmented by terms increasing 

 as the fourth and higher powers of the velocity through the 

 action of vertical disturbances of the water. 



XLIV. Notices respecting New Books. 



A Dictionary of Chemistry and the Allied Branches of other Sciences. 

 By Henry Watts, B.A., F.C.S. Vol. I. 8vo. pp. 1150. London : 

 Longman and Co., 1863. 



HP HE completion of the first volume of this work enables us to 

 ■*- form a more definite estimate of its general scope and plan, 

 as well as of the degree of success with which that plan is being 

 carried out, than could be formed from the first two Parts, a notice 

 of which was given in this Magazine four months ago (Phil. Mag. 

 for June 1863, p. 473). We then expressed the fear that the limits 

 assigned to the work would prove too narrow to allow of the latter 

 portions being treated with the same fulness of detail as the begin- 

 ning; we are therefore glad to find that it has been decided to 

 increase its size by nearly one-third, the intention now being to com- 

 plete the work in twenty- one, instead of sixteen, monthly parts, 

 making four volumes, which will together contain about 4000 pages. 

 Careful economy of the space thus gained will still be needed in 

 order to avoid the necessity of unduly curtailing the concluding por- 

 tions of the work. 



