OCR Text |
Show 490 On the 077' quointed Conn/21620". in from sort ones; Imean from fuch as {how the greateit length, above the hit/(1mg they are fixed on. EXPERIMENT III. Inftead of pinching the point between the thumb and finger, as in the 1.111 experiment, keep the thumb and finger each at Izmr (172 int!) dyz'mxre from it, but at the/[11m bright, the point between them. In this fituation, though the point is fairly expofed to the prime conductor, it has little or no effeét; the eleétrometer rites to the height of a full charge.-But the moment the fingers are tel/am [M. P.] firming Building:from Lightnin g. 491 electric-Hum in the point, oppofing its defcent, and (la/mg {/33 pawl" to retain 1t 1; contrary to the repelling power of the prime cond uctor, which would drive it down.-And this may alfo ferve to explain the diffi'l‘CHt powers of the point in the preceding experiment, on the flipp ing down the finger and thumb to different dittance s *. Hence is collected, that a pointed rod erected éetwem two tall c/az‘mm‘t'r, and very little high er, (an inf'tance of which I have feen) cann ot have {0 good an effeét, as if it had been erected on one of the chimneys, its whole length above it. away, the ball falls quick to the Item. Oé/i'rmztim. To explain this, it is fuppofed, that one reafon of the fudden efi‘ec‘t produced by a long naked pointed wire is, that (by the repulfive power of the pofitive charge in the prime conductor) the natural quantity of electricity contained in the pointed wire is driven down into the earth, and the point of the wire made firongly ncgaz‘zt'e; whence it attracts the eleétricity of the prime conduc‘tor more {trongly than bodies in their natural {late would do 5, thefilm/Z quantity qfcommmz 77ml- ter in the point, not being able by its attractive force to retain its natural quantity 9/ [/JL‘ c/rfirzc fluid, againft the force of that repullion.--But the finger and thumb being {ubi‘tantial and blunt bodies, though as near the prime conduetor, hold up better their own natural quantity'againft the force of that repulfion; and to, continuing nearly in the natural Rate, they jointly operate on the ' EXPERIMENT IV. If, {Mead of a long pointed wire, a large/Md éoafy, (to reprefent a building without a point) be brought under and as near the prime conductor, when charged; the ball of the eleétrometer will fall a little; and on taking away the large body, will rife again. Oéflrmtion. Its rg'flng again {hows that the prime conductor loft little or none of its eleétric charge, as it had done through the point: Thefiz/lz'ng of the ball while the large body was under the conductor, therefore {hows that a quantity of its atmofphere was drawn from the end where the eleétrometer I. [Perhaps their firtt and principal tendency is, to repel and thereby leffen the influence of the fluid in the waduflor. See the concluding note. E. " [If] remember well, the French tranflation of this paper in Illa/I. Dubourg's edition, requires fome revifion as to this paragraph. eleCtric Rrra is ‘lllllllllllllillllllllfillll |