. 
L.F. MENABREA ON BABBAGE’S ANALYLICAL ENGINE. 677 
combined together, the machine commences by effacing them 
from the columns where they are written, that is it places zero * 
on every disc of the two vertical lines on which the numbers were 
represented; and it transfers the numbers to the mill. There, 
the apparatus having been disposed suitably for the required 
operation, this latter is effected, and, when completed, the result 
itself is transferred to the column of Variables which shall have 
been indicated. Thus the mill is that portion of the machine 
which works, and the columns of Variables constitute that where 
the results are represented and arranged. After the preceding 
explanations, we may perceive that all fractional and irrational 
results will be represented in decimal fractions. Supposing each 
column to have forty discs, this extension will be sufficient for 
all degrees of approximation generally required. 
It will now be inquired how the machine can of itself, and 
without having recourse to the hand of man, assume the success- 
ive dispositions suited to the operations. The solution of this 
problem has been taken from Jacquard’s apparatus}, used for 
the manufacture of brocaded stuffs, in the following manner — 
Two species of threads are usually distinguished in woven 
stuffs; one is the warp or longitudinal thread, the other the 
woof or transverse thread, which is conveyed by the instrument 
called the shuttle, and which crosses the longitudinal thread or 
warp. When a brocaded stuff is required, it is necessary in 
turn to prevent certain threads from crossing the woof, and this 
according to a succession which is determined by the nature of 
the design that is to be reproduced. Formerly this process was 
lengthy and difficult, and it was requisite that the workman, by 
attending to the design which he was to copy, should himself 
regulate the movements the threads were to take. Thence arose 
the high price of this description of stuffs, especially if threads 
‘of various colours entered into the fabric. To simplify this 
manufacture, Jacquard devised the plan of connecting each 
group of threads that were to act together, with a distinct lever 
belonging exclusively to that group. All these levers terminate 
in rods, which are united together in one bundle, having usually 
the form of a parallelopiped with a rectangular base. The rods 
are cylindrical, and are separated from each other by small in- 
* Zero is not always substituted when a number is transferred to the mill. 
This is explained further on in the memoir, and still more fully in Note D.— 
Nore ny Transvator. 
+ See Note C, 
