7ft* Experiments for investigating 



probably a pair of bellows, constructed on purpose, will be 

 contrived, so as to prevent unnecessary loss of the sulphur. 



By the same friendly communication 1 have received fresh 

 assurances, not only of the powerful influence of sulphur as 

 a vermifuge against the whole tribe of worms and other in- 

 sects, which infest, and prey upon, vegetables ; but I also 

 find, that in other respects this substance is even congenial 

 to the health of those trees and plants on which it is sprin- 

 kled — that peach-trees in particular were remarkably im- 

 proved by the sulphur ; they absorbed it, and, it may be said, 

 Were even fond of it ; for it was evidently absorbed, and 

 must hive entered into the vegetable system. It was like- 

 wise noticed, that the verdure and other healthful appear- 

 ances were perceptibly increased ; for the quantity of new 

 shoots and leaves formed subsequently to the operation, 

 and having no sulphur on their surfaces, served as a kind of 

 comparative index, and pointed out distinctly the accumu- 

 lation of health. 



Upon the whole, it may be observed, that, independently 

 of its deleterious effects on the vermin, the question respect- 

 ing these sanative powers of such an insoluble substance as 

 sulphur, seems to be one of the utmost importance ; and, I 

 should think, must be highly interesting to the physiologist, 

 and, indeed, to all men of science. 

 \ remain, sir, 



your obliged and obedient servant, 



Long-Acre, Jos. HuME, 



Feb. 24, 1808. 



XVIII. Experiments for investigating^ the Cause of the co- 

 loured conctntriQ Rings, discovered bij Sir Isaac Newton, 

 between two Object- glasses laid upon o,ne another. By 

 William Herschel, I^LD, F.R.S.* 



J. jiE account given by Sir I. Newton, of the coloyred arcs 

 ^cl rings which he discovered by laying two prisms or ob- 



* From Philosophical Transactions fp.ir i807, Part 11. 



ject- 



