C 2 50 3 
XVIII. On a method of expressing by signs the action of 
machinery. By Charles Babbage, Esq. F. R. S. Com- 
municated January 17, 1826. 
Read March 16 , 182 6 . 
In the construction of an engine, on which I have now been 
for some time occupied, for the purpose of calculating tables 
and impressing the results on plates of copper, I experienced 
great delay and inconvenience from the difficulty of ascertain- 
ing from the drawings the state of motion or rest of any 
individual part at any given instant of time : and if it became 
necessary to enquire into the state of several parts at the 
same moment the labour was much encreased. 
In the description of machinery by means of drawings, it 
is only possible to represent an engine in one particular state 
of its action. If indeed it is very simple in its operations, a 
succession of drawings may be made of it in each state of its 
progress which will represent its whole course ; but this 
rarely happens, and is attended with the inconvenience and 
expence of numerous drawings. The difficulty of retaining 
in the mind all the cotemporaneous and successive move- 
ments of a complicated machine, and the still greater difficulty 
of properly timing movements which had already been pro- 
vided for, induced me to seek for some method by which I 
might at a glance of the eye select any particular part, and 
find at any given time its state of motion or rest, its relation 
to the motions of any other part of the machine, and if 
