196 ANNUAL OF SCIENTIFIC DISCOVERY. 



upper corner, is given to each large letter ; this is called the ' index of iden- 

 tity,' and all parts which are absolutely fixed to each other must have the 

 same index of identity ; no two parts which touch, or interfere with, or cross 

 each other, on the drawings, must have the same index- of identity. This 

 may generally be done without taking higher numbers than 9. All pieces 

 which are loose round an axis must have a letter of the same character, 

 Roman, Etruscan, or writing ; but a different index of identity will at once 

 inform us that it is a separate piece, and not fixed on the axis. I shall now 

 endeavor to explain how the transmission and action of one piece on another 

 is shown, beginning from the source of motion. Each part is written down 

 with its working points ; those of its points which are acted on are on the 

 left-hand side; those points where it acts on other pieces are on the right 

 hand ; if there are several, a bracket connects the small letters with the large. 

 The pieces being arranged, arrow-headed lines join each acting or driving 

 point of one piece with the point of another piece, which it drives or acts on. 

 It is usually necessary to make two or three additions when a machine is 

 complicated, before all the parts can be arranged with simplicity ; but, when 

 done, 'the trains,' as they are called, indicate with the utmost precision the 

 transmission of force or motion through the whole machinery, from the first 

 motive power to the final result. It is, however, one of the principles of the 

 notation to give at one view the greatest possible amount of information, so 

 long as no confusion is made ; and it has been found that without in any way 

 interfering with the simplicity of 'the trains,' a great deal more information 

 may be conveyed. For instance, while looking at 'the trains,' it is often con- 

 venient or necessary to know something of the direction of the piece under 

 consideration, and, by the use of a few signs placed under the large letters, 

 we can convey nearly all that is wanted in this respect. Again, though the 

 drawings of a machine are specially intended to give the size and shape of 

 each piece, yet by the use of some signs of form which are placed over the 

 letters, the shape of each piece may be indicated. It is found that these signs 

 do not confuse the trains ; but on the contrary, extend their use by making 

 the information they convey more condensed, and more easily accessible. I 

 now pass to ' the cycles' as they are termed, or to that part of the notation 

 which relates to the tune of action of the different parts of a machine. ' The 

 cycles' give the action of every part during the performance of one complete 

 operation of the machine, whatever that may be. Each piece has a column 

 of its own, and the points by which it is acted on are placed on its left hand, 

 and the points by which it acts on other parts are placed on its right ; and 

 each working point has also its own column. The whole length of the 

 column indicates the time occupied in preparing one operation, and we divide 

 that time into divisions most suited to the particular machine. During each 

 division of time that a piece is in motion, an arrow up and down its column 

 indicates the fact ; and during the time of action of each working point, aji 

 arrow in its column shows the duration of its action. The times thus shown 

 are, of course, only relative and not absolute time ; but it would be easy to 

 show both, by making the divisions of the column correspond with the num- 

 ber of seconds or minutes during which the machine performs one operation. 



