BOOK NO TICES. 669 



Knight's New Mechanical Dictionary. Section III. Edward H. Knight, 

 A. M. LL.D.; octavo, pp. 240. Houghton, Mifflin & Co., Boston; $2.00. 



It is a fortunate thing for the subscribers to this valuable work that its author 

 had fully completed it before his death, which occurred but a few weeks since, 

 for we know of no one who could have successfully taken up and finished the 

 task. As it is, the publication of the successive volumes will be slightly delayed 

 — a few weeks at most, however — by reason of the proofs having to be read with- 

 out the author's assistance. 



The volume extends from the monstruttt horrendum participle '' Hydraulick- 

 ing" which is the " short " among miners for washing down a placer claim by 

 means of a hose or giant nozzle, to Printing Press, including descriptions of all 

 kinds of hydraulic apparatus, ice machinery, laboratory apparatus, leather and 

 its imitations, locomotives, magazine guns, marine engines, metallurgy, micro- 

 scopes, mill machinery, mowers, nautical instruments, oil-stoves, oyster culture, 

 pavements, phosphor bronze, photography, pile-drivers, plate machinery, pneu- 

 matic apparatus, porcelain manufacturing, portable engines, etc. Every page 

 contains elaborate illustrations of the machines described, and with all the import- 

 ant titles are given references to full descriptions in other works. Thus, under 

 the title "locomotive" more than three hundred references are made to articles 

 upon various branches of the subject in the Engineer, Scientific American, Manu- 

 facturer and Builder, Thurston's Vienna Reports, Van Nostrand^ s Magazine, Le 

 Technologiste, Railroad Gazette, etc. 



It seems impossible to think of an appropriate subject that has been omitted 

 and in most cases the treatment is full, clear and exhaustive. The printing and 

 engravings are exceedingly well done. 



The Theory of the Gas Engine. Dugald Clerk; i8mo. , pp. 164; Illustrat- 

 ed. D. Van Nostrand, New York; 50c. 



After pointing out the inefficiency of steam engines, the best of which do not 

 credit more than ten per cent of the heat used by them into work and many of 

 them not over four per cent, and the impracticability of gas engines, notwith- 

 standing their apparent compHance with all necessary conditions, the author pro- 

 ceeds to show that the gas engine presents the best prospect of satisfactory results. 

 He names three well defined types of engines that have been proposed. 



1. An engine drawing into its cylinder gas and air at atmospheric pressure 

 for a portion of its stroke, cutting off communication with the outer atmosphere, 

 and immediately igniting the mixture, the piston being pushed forward by the 

 pressure of the ignited gases during the remainder of its stroke. The in-stroke 

 then discharges the products of combustion. 



2. An engine in which a mixture of gas and air is drawn into a pump, and 

 is discharged by the return stroke into a reservoir in a state of compression. From 

 the reservoir the mixture enters into a cylinder, being ignited as it enters-, without 



