4l6 ^ PHILOSOPHICAL TRANSACTIONS. [aNNO I767. 



XIX. Descnpiion of an improved Apparatus for performing Electrical Experi- 

 ments, in which the Electrical Power is Increased, the Operator Entirely Se- 

 cured from receiving any uiccidental Shocks, and the whole rendered more 

 Convenient for Experiments than heretofore. By C. UEpinasse, F.R.S. 

 p. 186. 



The first method of improvement consists in lining the inside of the glass 

 cylinder or globe with the following composition. Take 4 lb. of Venice turpen- 

 tine, 1 lb. of resin, 1 lb. of bees' wax; boil these over a gentle fire, stirring them 

 now and then, for about 4 hours, at the end of which stir in a quarter of a pound 

 of vermilion : then, a little of the mixture being taken out and left to cool, will 

 be hard and brittle ; a token that it is fit for use. Having well heated the globe 

 or cylinder, pour the melted mixture into it; turn the cylinder about so as to 

 spread it evenly over the inside surface to the thickness of a sixpence, and let it 

 cool very gradually. 



A cylinder thus lined acts with much greater force than it did before it was 

 lined, every other circumstance alike. And as a small cylinder thus prepared is 

 equal in power to one much larger, that is not, and requires less friction, the 

 apparatus in which it is mounted may be much contracted, and the whole, to- 

 gether with the person that turns the machine, may be easily supported on one 

 or two small stools with glass feet, when experiments require it. 



As raising the greatest quantity of electrical fire was the object of the first im- 

 provement, the next thing was, to preserve it when raised, and use it without 

 wasting any, so that it might have its full effect. Mr. L. had observed, that 

 whenever a single wire was made use of instead of a chain in discharging the jars, 

 the effect was much stronger ; and on making further experiments, he found that 

 when the discharging parts were not all in close contact, such as being screwed 

 tight together, or ground into one another, the effect was considerably dimi- 

 nished. In constructing the discharging apparatus, he therefore contrived that 

 all the parts should be in close contact, by screwing, grinding, or soldering, 

 them together ; and thus the electrical fire exerts its whole force on the body on 

 which the experiment is made. Lastly, it often happened in discharging the jars 

 ' when loaded very high (as they must be to kill a large animal, or to force the fire 

 through bodies that make a great resistance), that the persons operating, notwith- 



and small quantities, to render the calculation easier. It further appears that an accurate determination 

 of that distance is not even to be expected on the same principles as here employed. On this sub- 

 ject, see two pamphlets, the first in 176,9 by Mr. Dawson of Sedberg, but without his name, entitled 

 "Four Propositions, &c.;" and the other by Mr Landen, in 1771, entitled "Animadversions on 

 Dr. Stewart's Computation of the Sun's Distance from the Earth." See also an account of Dr. Slew- 

 art's Life in the 1st vol of the Edinburgh Phil. Trans. 



