On the Electric Fhtid. 173 



cord, covered with canvas, and painted in oil, so as to 

 make it water-proof. 



BB arc tapes or cords about two feet long fastened to 

 the back of the girdle with loops at the ends. 



C is another tape or cord about three feet long, in the 

 njiddle of which a few corks arc strung, covered with can- 

 vas, and painted as above. 



D is a pin of hard wood three inches long and half an 

 inch diameter, fastened to the front of the girdle bv a tape 

 or cord about two inches long. 



E the same. 



When the marine spencer is to be used, slide it from the 

 feet close up under the arms ; bring the tapes or cords B B 

 one over each shoulder, and fasten them by the loops to the 

 pin D ; bring the tape or cord C between the legs, and fasten 

 it to the pin E. 



A person thus equipped, thovigh unacquainted with swim- 

 ming, may safely trust himself to the waves ; for he \\ ill 

 float head and shoulders above water in any storm, and by 

 paddling with his hands mav easily gain the shore. 



N.B. A marine spencer constructed as above, and co- 

 vered v.ith strong eanvas unpainted, will have nearly the 

 Same buoyancy, though more liable to damage from the 

 effects of sea water. 



XXIX. On the Ekcttic Fluid*. 



J. HE hypothesis of the electric phaenomena being caused 

 by tuo fluids is now ncarlv given up for the more simple 

 one of a single fluid. Cavallo in his Treatise on Electricity, 

 4th edit. vol. i. p. 106, luj, says: " When a body does 

 not show any electrical appearances, it is then supposed to 

 contain its natural quantity of electric fluid (but whether 

 that quantity bears any proportion to the quantity of matter 

 in general or not, is uncertain, and therefore that body i^ 

 said to be in its natural or mm-etevtrificd state) : but if a 

 body shows any electrical appearances, it is then said to be 

 electrilicd, and it is supposed that it has eitlier acquired an 

 additional quantity of electric fluid, or that it has lost some: 

 of its natural share. A bodv having received an additional 

 quantity of electric fluid is said to be overcharged, or posi- 

 tively eleclrijitid ; and a l)()dy that has lost part of its natural 

 quantity of electric fluid is said to be undercharged, or Tiega' 



'* Communicated hy a Friend to Physical Inquiries. 



tiveli/ 



