On Plaisfer of Paris. 117 



5. On two others, ashes or lye. 



The common salt must be applied at a distance 

 from the gyps ; plaister does not succeed on sea coasts, 

 where the air is always impregnated with sea salt. 

 This salt and that in plaister, by operating on each other, 

 may change the qualities of both. Sulphuric acid forms 

 sulpJiat of soda, or glauber salts, by decomposing ma- 

 rine salt, and combining with the soda. Glauber salts , 

 and all compounds containing sulphuric acid, are ma- 

 nures, or auxiliaries to vegetation: but are not so effec- 

 tual or cheap as the gypsum. The small quantities re- 

 quired of the latter, and its rapid decomposition, will 

 always give it the preference. 



R. P. 



6. Sprinkle, on two other lands, water, in which of/ of 

 vitriol is dissolved : this water will kill, or banish, bugs, 

 flies, and other insects, from bedsteads, walls, Sec, in our 

 houses. If the plaister is an enemy to the fly, it is pro- 

 bably by means of its vitrolic acid. If this could be 

 proved by experience, Ingenhausz would render es- 

 sential service, by his theory of the oil ofvitrioL 



It would be well, if several farmers were to try some 

 experiments of this sort; though at first they may seem 

 whimsical. My fields, generally plaistered on the wheat, 

 or on preceding crops of grain and clover, have been 

 little infested by the fly. But I have attributed the 

 safety of my wheat, to good tilth and manure. So that 

 the crop may be soMai late, and the ground throw up 

 strong and vigorous plants, which resist the fly, when 



