USEFUL PROJECTS. 



387 



tracted from the tobacco, but is 

 mixed, by the tobacco manufac- 

 turers, with cold water, in the pro- 

 portion of four or five pints of 

 water to one of the original juice 

 Or essence. Therefore, any person 

 who may purchase the juice itself, 

 unmixed, must mix it with water in 

 the above proportion; and the quan- 

 tity of alum must be about an ounce 

 for each Scots pint of the mixture. 

 Dr. Monro's report was in the 

 following words : " I observed, 

 along with Mr. Hamilton and Mr. 

 Gordon, (two other gentlemen of 

 the committee) and two gardeners 

 who were present, that such cater- 

 pillars as were wetted by the liquor 

 Mr. Henderson employs, were killed 

 in a very few minutes ; and the ex- 

 periment has been repeated by my 

 own gardener, with the same effect. 

 I have likewise found, that it kills a 

 kind of green fly, which is very 

 hurtful to the leaves of plumb-trees 

 and other fruit-trees. It has been 

 very generally known, that the 

 smoke and the juice of tobacco were 

 pernicious to different kinds of in- 

 sects and worms ; but it has not, so 

 far as I know, been employed in 

 Mr. Henderson's manner ; and, as 

 this has the advantage of not hurt- 

 ing the leaves, nor the fruit, I con- 

 sider it as an useful and material im- 

 provement, and well entitled to a 

 moderate premium." 



Account of some Experiments made 

 in France, respecti7ig the Quality 

 of Pewter, by M. Coquebert ; 

 read at the Council of Weights 

 and Measures, 



SOME new regulations about to 

 be made, with respect to the 

 pewter measures which are usedfor 



wine, vinegar, and several other 

 liquors, rendered it necessary to 

 take into consideration the two fol- 

 lowing circumstances respecting 

 that metal : 



First. To determine what degree 

 of purity pewter should possess, in 

 order to render it fit for the uses 

 above-mentioned, without any risk 

 to health. 



Secondly. To discover some sim- 

 ple and easy means by which the 

 quality of pewter might at any time 

 be ascertained, without injury to 

 the vessels made of it. 



In consequence thereof, MM. 

 Legendre, Gattey, and Coquebert, 

 members of the council of weights 

 and measures, proposed, some 

 months ago, to the government, that 

 a plan of inquiry should be under- 

 taken, in conjunction with MM. 

 Gillet, Lefevre, and Lelievre, 

 members of the council of mines, by 

 which the solution of the above 

 questions might be accomplished. 



These commissioners desired to be 

 assisted by M M. Fourcroy, Vauque- 

 lin, and Dillon ; and, after a great 

 number of delicate experiments, 

 made with the greatest care, by the 

 united labour of the forementioned 

 gentlemen, many new and interest- 

 ing facts were ascertained, which 

 have served to fix the opinion of the 

 government, with respect to those 

 points which were the objects of 

 this inquiry. 



The experiments of the above 

 gentlemen have proved. 



First. That tin is more easily dis- 

 solved than lead, and is dissolved 

 sooner than lead, by the action of 

 wine, or of vinegar. 



Secondly. That lead is not sensi- 

 bly oxidated by the above liquors, 

 except at the line of contact of the 

 air and the liquor: consequently, 



Cc2 



