si6 Mr. Hatchett's analytical Experiments 
melting it, and mixing with it about three parts of sand. For 
making polishing grindstones, the sand is sifted through fine 
muslin; but those which are employed by the lapidaries, are 
formed with powder of corundum, called by them Corune.* 
But, in addition to all the above uses to which it is applied 
in India, as well as to those which cause it to be in request in 
Europe, Mr. Wilkins's Hindu ink occupies a conspicuous 
place, not merely on account of its use as an ink, but because it 
teaches us to prepare an aqueous solution of lac, which probably 
will be found of very extensive utility. 
This solution of lac in water may be advantageously em- 
ployed as a sort of varnish, which is equal in durability, and 
other qualities, to those prepared with alcohol ; whilst, by the 
saving of this liquid, it is infinitely cheaper. 
I do not mean however to assert that it will answer equally 
well in all cases, but only that it may be employed in many. 
It will be found likewise of great use as a vehicle for colours ; 
for, when dry, it is not easily affected by damp, or even by 
water. 
With a solution of this kind, I have mixed various colours, 
such as, vermillion, fine lake, indigo, Prussian blue, sap green, 
and gamboge ; and it is remarkable, that although the two last 
are of a gummy nature, and the others had been previously 
mixed with gum, (being cakes of the patent water-colours,) yet, 
when dried upon paper, they could not be removed with a 
moistened sponge, until the surface of the paper itself was rubbed 
off. 
In many arts and manufactures, therefore, the solutions of 
* Phil. Trans, 1781, p, 380. 
