as the former is distinctly hard to guide well.

I think, then, we should be safe in saying that the error of the
integraph is not likely to be greater and is probably less than 2 per
cent., so that in this respect the instrument may be considered a
practical one.

5. A further condition for a good integraph is that it should have a
wide range of polar distances, and that it should be easily set at
those distances.

One of the conditions I gave to the maker of the instrument was that
it should be able to take all polar distances from one to ten
half-inches. This condition he can scarcely be said to have fulfilled.
With polar distances of 1/2 inch and 1 inch, the machine works
unsatisfactorily, which indeed might have been foreseen from the
construction of its sliding bars. It works best from 2.5 inches to 5
inches, and this is the range to which I think we ought to confine the
present type of instrument. As the last conditions I may note that:

6. A practical integraph ought to be easy to read.

7. Draw a good clear curve.

The scale on the present instrument is very inconvenient, as it is
often almost out of sight; the curve it draws, on the other hand, I
consider very satisfactory, when the pencil is loaded, say, with a
planimeter weight. On the whole, I think you will agree with me that
this integraph goes a good way, if not the whole way, toward
fulfilling the conditions of a practical instrument.