11. The next confiderable Improver of Electricity was Mr. Stephen Gray, of the Charter-house, who spent no small part of his Time in making fuch kind of Experiments, ftill improving on Mr. Haukfbee's glass Tube; but tho' we never heard that he made use of the revolving Globe or Cylinder, as Mr. Haukbee did, yet he carry'd his Researches much farther than he, and from the great number of Experiments made by him, he may truly be faid to have fet on foot all the Discoveries that have been fince made on that curious Subject.

12. Dr. Defaguliers in the 1ft Vol. of his Courfe of experimental Philofophy, p. 450, tells us, that Mr. Gray had made a greater variety of electrical Experiments than all the Philofophers of this and the last Age*.— It was he who difcover'd that Glafs, Amber, Refin, Wax, Silk, Hair, and all other electric Bodies, did not convey the electric Matter to other Bodies, nor fuffer it to escape thro' them like Metals, Water, Animals, and some others, and confequently if he fupported the latter with the former, he might convey it to diftant parts; this discovery was productive of

Notwithstanding this is true, and tho' the World is greatly indebted to him for fuch indefatigable Pains and Induftry; yet it must be own'd, that it is much more indebted to Mr. Haukfbec for pointing out the means.

ano

another, viz. that fuch propagation of it to diftant Bodies feem'd inítantaneous, he himself having experienc'd it to be fenfibly fo, to the distance of 800 feet.

13. It was he who difcover'd it to escape into the Earth, and having likewise discover'd, that what are fince call'd electrics per fe would prevent fuch escape, his method was to fufpend a Perfon horizontally on two hair or filk Lines, then rubbing his glafs Tube, and holding it near his Feet, his Face or Hands were inftantly capable of attracting and repelling light Bodies.

14. He afterwards discover'd that more commodious method of electrifing a Perfon, viz. By setting him on a Cake of Refin, Glafs, or any other electrical Substance, and that it was equally the fame as fupporting him with hair or filk Lines.

15. A greater Improvement yet, was the introducing of the glafs Globe, Cylinder, and Spheroid whirling on their Axes, instead of rubbing the glass Tube, the Power being by that means increas'd to a very high Degree.

16. Thus having brought it to fuch Perfec tion, a great Number of various Experiments were every where made, particularly after it was discover'd fo plainly to be Fire, as to kindle up many particular Bodies into an actual Flame.

17. But the greateft Improvement of all, and what conducted to the finishing Stroke,

was

was the accidental and furprising Shock, difcover'd to Profeffor M. de Mufchenbroek of Leyden: An Account of which was communicated in a Letter from Paris, and was as follows:

18. March 25th 1746. M. de Mufchenbroek, a famous Profeffor of experimental Phyfics at Leyden, has wrote a Letter to M. de Reaumur, of the Royal Academy of Sciences, containing an Account of a very fingular Experiment, which has led him to feveral Difcoveries concerning Electricity.

The

EXPERIMENT.

19. Having fufpended an iron "Cannon horizontally, upon filken Cords, with one end near the electrical Globe, he faftened to the other end a latten Wire, which defcended into a Bottle half full of Water; that holding up the Bottle with one Hand, while the Cannon was electrifing, he put forth a Finger of his other Hand towards the Piece, in order, as ufual, to draw off a Spark, but was ftruck fuch a violent blow, that he thought his Life was at an end; and adds, that, esteeming himself very happy in efcaping, he had no mind to repeat the Experiment, and that the Commotion he felt was like a Clap of Thunder.

20. As this Letter came at a Time when

many learned Men were employ'd about Electricity, the Abbe Nollet and M. de Monniers

Monniers, of the fame Academy, zealous to fearch into fo extraordinary a Phænomenon, divefted themselves of Fear, made the fame Experiment as M. de Mufchenbroek had done, and, in like manner, found the Commotion very terrible.

London Evening Poft, April the 1ft, 1746.

21. This fudden and wonderful Discovery amazed the whole European World a confiderable time; for before this, very little, if any Power or Force was perceiv'd in Electricity or even fufpected; fo that now it appear'd fo much to exceed the Power of what was found in it before, as to bear scarcely any Manner of Proportion; for inftead of being strong enough to be felt to push against the Finger (which, before this, was counted a great Matter) it was now found much more capable of moving a Mountain, and, from the great Number of Experiments which were foon made in all Places, the Progrefs of its clearer and clearer Discovery was, from that Time, exceedingly rapid. -Having myself clearly difcovered, by a repeated Courfe of Experiments,' that Air is a principal Agent in producing those wonderful electrical effects, which have of late years fo juftly engag'd the attention of the curious, it naturally conducted me, who have devoted a confiderable portion of my time. to thofe Studies, (particularly, fince Profeffor Mufchenbroek difcover'd the above-mentioned wonderful force of the electrical fluid) to en

quire more particularly into the nature, properties, and conftituent parts of the Atmofphere, or common Air; and as Chambers in his Dictionary gives us the Sentiments of the most approv'd Writers on that Subject, I apply'd to him, who informs us,

22. That Air in Phyfics, is a thin fluid, transparent, compreffible and dilatable Body, furrounding the terraqueous Globe to a confiderable height.'

23. 'Air was confider'd by fome of the Ancients, as an Element, but then by • Element they understood a different thing from what we do.'

24. 'Tis certain that Air taken in the popular fenfe is far from the fimplicity of an elementary fubftance; tho', there tho', there may be fomething in it which bids fair for the appellation. Hence Air may be distinguish'd into vulgar or heterogeneous, and proper or elementary.'

25. Vulgar or heterogeneous Air is a coa⚫lition of corpufcles of various kinds, which together constitute one fluid mafs, wherein < we live and move, and which we are continually receiving and expelling by respiration; ⚫ the whole affemblage of this makes what we call the Atmosphere.'

26. The fubftances whereof Air confifts, may be reduc'd to two kinds, viz. First, the Matter of light or fire: Secondly, thofe ⚫ numberlefs particles, which in form either

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