428 PHILOSOPHICAL TRANSACTIONS. [aNNO 1794, 



It may very probably be thought right, for the future use of the revenue, to 

 compute another set of tables, in which the degree of heat standing at the head 

 of each table, the first column of it shall be even numbers of specific gravity. 

 This would be proper for looking out at once the quantities of spirit and water 

 in a mixture, from its heat and specific gravity, as immediately determined by 

 experiment. For scientific purposes also, tables should be constructed to show 

 the regular increments and decrements of the concentration, by equal variations 

 in the proportions of spirit and water : but these, and others of a similar nature, 

 which might be suggested, do not belong to the present subject. C. B. 



The tables, which are very voluminous, are unnecessary to be retained in these 

 abridgments. 



XXI. Observations and Experiments on a JVax-lihe Substance, resembling the 

 Pe-la of the Chinese, collected at Madras, by Dr. Anderson, and called by 

 him JVhile Lac. By George Pearson, M. D., F. R. S. p. 383. 

 1. Some observations relative to the natural history of the insect which secretes 

 a sort of wax, called ivhite lac. — The matter which is the subject of the follow- 

 ing observations and experiments was first noticed by Dr. Anderson, of Ma- 

 dras, about the year 1786, in a letter to the governor and council of that place, 

 when he says, nests of insects resembling small cowry shells were brought to 

 him from the woods by the natives, who eat them with avidity. These supposed 

 nests he shortly afterwards discovered to be the coverings of the females of an 

 undescribed species of coccus ; and having noticed in the Abbe Grosier's account 

 of China, that the Chinese collect a kind of wax, much esteemed by them, 

 under the name of pe-la, from a coccus deposited for the purpose of breeding on 

 certain shrubs, and managed exactly in the same manner as the Mexicans 

 manage the cochineal insect, he followed the same process with his new insects, 

 and shortly found means to propagate them with great facility on several of the 

 trees and shrubs growing in his neighbourhood. 



On examining the substance, he observed in it a very considerable resemblance 

 to bees-wax ; and noticed that the animal which secretes it provides itself with a 

 small quantity of honey, resembling that produced by our bees ; and he com- 

 plains in one of his letters, that the children whoin he employed to gather it 

 were tempted by its sweetness to eat so much of what they collected, as to dimi- 

 nish materially the produce of his crop. It is also believed that the white lac 

 possesses medicinal qualities. A small quantity of this matter was sent to the 

 President in I78g ; but as there was not enough for the various experiments 

 which suggested themselves to chemists who were consulted on the occasion, he 

 wrote to Dr. Anderson for an additional quantity, who in 179^ furnished him 

 with some pounds of it, both in its natural state, and melted into cakes, as also 

 of the insects adhering to the branches on which they had been cultivated. 



