273 



neutral combination with sulphuric acid, and that the compound in 

 its purest known form constitutes what has been called oil of wine ; 

 and that when in this state it is acted upon by certain salifiable 

 bases, a portion of the hydrocarbon is thrown off, and a distinct set of 

 neutral salts formed, which are resolvable by heat into bi-sulphates; 

 and which therefore include two proportionals of the elements of 

 sulphuric acid, one of proto-carburet of hydrogen, and one of base. 



On a Method of expressing by Signs the Action of Machinery. By 

 Charles Babbage, Esq. F.R.S. Communicated January 17, 1826. 

 Read March 16, 1826. [Phil. Trans. 1826, p. 250.] 



In the construction of an engine for calculating and printing ma- 

 thematical tables, in which the author of this paper has been for 

 some time occupied, he states himself to have met with considerable 

 difficulty from the want of any method by which all those motions 

 which take place in any machine at the same instant, may be easily 

 perceived and referred to, and by which the movement of any part 

 might readily be traced back, through all the intervening stages, up 

 to the first mover of the machine. The usual modes of mechanical 

 drawing he found quite insufficient for these purposes, except in ma- 

 chinery of the simplest construction ; and, even if they had not al- 

 together failed in more complicated cases, the time and expense 

 required for their execution would have effectually prevented their 

 employment. 



The most important question was to contrive some method by 

 which all the simultaneous movements, occurring at any moment, 

 should be at once visible ; and the history of the state of motion or 

 rest of any given part should be apparent during the whole cycle of 

 the action of the engine. The author had therefore recourse to a 

 system of signs, which bear an analogy to those employed in alge- 

 bra, whilst they differ from them by having a general resemblance to 

 the things they are intended to represent. Having gradually found 

 that this system, which he calls " mechanical notation," was readily 

 susceptible of affording other information than that for which it was 

 at first contrived, he was led to give to it additional extension. 



In its present form it gives, almost at a glance of the eye, infor- 

 mation relative to any of the following points. 



The names of every part of any engine being written at the top 

 of the paper : 



1 . Its representations in all the drawings will be pointed out. 



2. The number of teeth in any wheel, pinion, or sector will be 

 seen. 



3. The actual angular velocity will also appear. 



4. The mean angular velocity will also appear. 



5. The origin of the motion of each part will be seen, and thus 

 the cause of its motion will be traced up to the first mover. 



6. At each transfer of movement, the method by which it was 



