Let me here lay down the conditions which seem essential to a
practical integraph. These are, I think, the following:
1. The price must be such that it is within the reach of the ordinary
draughtsman's pocket. The Amsler's planimeter at L2 10s. or L3 may be
said to satisfy this first condition. The price for the first complex
integraph designed by Coradi was L24 to L30. The modified form in
which I show it to-night is estimated to cost retail L14. Till an
equally efficient instrument can be produced for L5 I shall not
consider the price practical. If the error of its reading be not
sensibly greater than that of a planimeter, it is certainly worth
double the money.
2. The instrument must not be liable to get out of order by fair
handling and a reasonable amount of wear and tear. I cannot speak at
present with certainty as to how far our integraph satisfies this
condition; it is rather too complex to quite win my confidence in this
respect.
3. It must be capable of being used on the ordinary drawing board, and
of having a fairly wide range on it, i.e., it must not be limited to
working where the primitive is at one part only of the board.
Pages:
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31