114 Mr. Howard Grubb, 



more conversant with the principle and practical working of the 

 system. They may, however, be classified into three heads : — 



(a). The designing of the machine. 



(b). The working out of the details of construction. 



(c). The putting together of the machine. 



(a). Let us first consider the designing of the machine. What- 

 ever difficulties there are in understanding the working of 

 a complicated machine from accurate drawings made after the ma- 

 chine is completed, or even from the machine itself, much greater 

 are the difficulties to be encountered in designing the machine, for 

 in this case the designer has neither machine nor drawings to 

 guide him, and the only representation of the machine lies in his 

 own brain; while, therefore, he mentally plans one part, he has to 

 keep in his mind (if he can) the relative positions and actions of 

 all the other parts, and frequently to go back in his work and 

 modify and remodify various parts in his mind's eye, and all 

 this must be thought out before he puts pen to paper; for after 

 all, mechanical drawings represent, not the actions and motions 

 of the machine but the appliances (levers, wheels, cams, dfca), by 

 which these motions are produced. We cannot plan these appliances 

 before we know what is required for each part to do. 



What we do want, therefore, is a means of graphically repre- 

 senting the various motions and actions of the machine without 

 reference, in the first place, to the nature of the mechanical 

 appliances by which these various motions and actions are effected. 

 I have said enough I think to show that this part is most ad- 

 mirably fulfilled by this system of notation, for as the designer 

 plans motion after motion, and action after action, he represents 

 the nature, direction, quantity, and quality of each by these 

 various curved lines, and can go backwards and forwards touching 

 up and modifying the various actions (without taxing his brain 

 to carry the nature of all or any one of these actions), until he 

 gets all to his satisfaction, and in proper sequence. 



(6.) The next task of the designer is that of working out the 

 details of construction of the machine, and here again the system 

 assists him, for he can decide from the nature of the curve on his 

 chart (which curve he has before decided on to be the best 



