120 Answer to Question addressed to the Rev. J. Grooby. 
Having first cleaned your hone with a sponge, soap and water, 
wipe it dry; then dip the soap in clean soft water, and wetting 
also the hone, rub the soap lightly over it, until the surface is 
thinly covered all over; then proceed to set in the usual way, 
keeping the soap sufficiently moist, and adding from time to time 
a little more soap and water, if it should. be necessary. Observe 
that the soap is clean and free from dust before you rub it on 
the hone; if it should not be so, it is easily,;washed clean. Strop 
the razor after setting, and also again when you put it by, and 
sponge the hone when you have done with it. 
The preference due to Mr. Reveley’s method over the use of 
oil is certified by practical gentlemen; viz. Messrs. Wm. West, — 
W. H. Pepys, Richard Long, and Isaac Fremer. 
A paste or powder for razor strops, very superior to emery, 
plumbago, and other things commonly used, has been discovered 
in Paris by M. Merimée. _ It is the crystallized tritoxide of iron, 
called by mineralogists Specular Oligiste Iron. ~ It is a mineral 
substance, but an artificial oxide of equal fitness for the purpose 
may be made thus: ake equal parts of sulphate of iron (green 
copperas) and common salt. Rub them well together, and heat 
the mixture to redness in a crucible. When the vapours have 
ceased to rise, let the mass cool, and wash it to remove the salt, 
and when diffused in water, collect the brilliant micaceoys scales 
which first subside. These, when spread upon leather, soften 
the edge of a razor, and cause it to cut perfectly. 
XXXI. Answer to the Question addressed to the Reverend 
J. Groosy in our last Numler. [See p. 50.] 
To Dr. Tilloch. 
Cirencester, Feb. 12, 1822. 
Sie, — I see to inform the gentleman who asks, From what 
tables of M. Bessel I took the corrections for Dr. Maskelyne’s 
stars? that it was from the same he allndes to; namely, from 
those annexed to the first part. of the Konigsberg observations. 
From the specimen your correspondent has given of /is method 
of ascertaining the corrections, 1 am not at all surprised at his 
numbers differing from my own, nor at his hence concluding that 
I had fallen into some error; but I am rather surprised that his 
self-confidence should have led him to make the strange and un- 
warrantable assertion, that the Professor has not made use of his 
own tables in reducing his observations. 
Your correspondent tells us that, in everyinstance in which he 
has used the tables, he has found his results to differ, not only 
from those of another individual, but also from those of the au- 
thor himself; and he hence concludes, not very modestly J must 
5; say, 
