BOOK NOTICES. 253 



reference upon mechanics now extant, as none of them cover the period men- 

 tioned. 



The description of tools, instruments, mechanics, processes, engineering 

 devices, etc., are full and exact, more so than ordinary, from the fact that the 

 author was formerly an examiner in the U. S. Patent Office, and thus acquired a 

 critical habit of looking into the mechanism and merits of devices presented for 

 patenting. 



The same method has been adopted in dealing with the subject matter in both 

 works. First, each article appears in its proper alphabetical place, thus fulfilling 

 the function of a dictionary in affording direct response to inquiry. Second, 

 the items of information thus distributed throughout the work are classified in 

 special indexes of the art, profession, or manufacture to which they pertain. 

 The book thus fulfills the function of a Cyclopaedia, which is a collection of 

 treatises. 



"An index to a dictionary"' may seem a novelty or even a superfluity to the 

 reader of this notice, but when he comes to examine this work he will find that 

 the value of a work of reference depends largely upon its index Doctor Knight 

 has invented a system of what he terms " Specific Indexes," by the use of which 

 the inquirer is guided straight to the information he is in quest of, even though 

 he may be entirely ignorant of the name of a thing, and have but the most vague 

 and general notion of its use. This is accomplished by grouping under the gen- 

 eral title of each Science, Art, Trade or Profession a list or " Specific Index " of 

 €very article in the book bearing any relation to the subject in question. The 

 titles of these Indexes are in turn grouped at the beginning of the book, so that 

 by a glance one may determine which clew to follow. 



Besides the use above mentioned, these Specific Indexes afford the reader 

 an excellent opportunity for investigating thoroughly all that pertains directly or 

 indirectly to any special subject, by using the index under the title of that sub- 

 ject as a sort of starting point, and followmg out its various branches through all 

 their ramifications. 



Special attention is called to a new and valuable feature in the work, by 

 means of which exhaustive information upon any subject is placed within easy 

 reach. The author has made a complete Index to Technical Literature, covering a 

 period of five years, and embracing all English and American technical journals 

 published from 1876 to 1880 inclusive. Under title of each subject maybe found 

 a complete list of every article which has apppeared during this period in the 

 columns of these periodicals, and as every subject of importance has been thor- 

 oughly discussed therein, it is evident that the whole range of recent investigation 

 is placed at easy command. This Index cannot fail to meet with the heartiest ap- 

 preciation among those who have experienced the labor and difficulty attending 

 an exhaustive search upon any line of inquiry. 



The work treats of many thousand subjects, and is illustrated with over 

 2,500 carefully prepared engravings and numerous full-page plates, and for gen- 

 eral typographical excellence, quality of paper and printing it is unsurpassed. It 



