538 PHILOSOPHICAL TRANSACTIONS. [aNNO 1732. 



only in wet weather, the attractions are not made at so great a distance, as in 

 fair weather. 



Number 20 is a cake of sulphur that was melted ; and as the other bodies 

 have taken the form of a convex section of a sphere, this, when cold, was laid 

 with its flat side downwards, on the same table with the cone of sulphur : they 

 were both placed so near the wall, as to prevent the sun shining on them. This 

 was on the 1 8th of April ; and though it had no manner of cloathing or cover- 

 ing, has attracted ever since. And in this, as in the other bodies, the attraction 

 will be according to the weather ; but when it attracts the strongest, it is not 

 more than the 10th part of what the cone of sulphur, that is covered, at- 

 tracts. 



The manner of observing these attractions, is best performed by holding the 

 attracting body in one hand, and a fine white thread tied to the end of a stick, 

 in the other ; by this means, far less degrees of attraction will be perceived, 

 than by making use of leaf-brass. When the thread is held at the utmost dis- 

 tance, it may be attracted ; the motion of it is at first very slow, but still ac- 

 celerating as it approaches nearer to the attracting body. 



With a small hand air-pump he has made experiments on several bodies, and 

 finds that they will attract in vacuo, and that at very nearly the same distance 

 as in pleno, provided that the experiment be made in the same receiver filled 

 with air ; as will appear by the following experiments. 



There was taken a hollow glass sphere, of rather more than 2^ inches dia- 

 meter, being first excited. It was suspended by a loop of silk that went through 

 a small cork, with which the hole in the glass ball, by which it was blown, was 

 stopped, and by the loop suspended a small hook that was screwed on to the 

 brass wire that came through the collar of leather in the brass-plate that covered 

 the top of the open receiver ; as in the experiment of letting fall the guinea 

 and feather in vacuo. Then the ball was drawn up to the top of the receiver, 

 and the top of the small stand, covered with paper, was laid on the wet leather 

 on the plate of the pump, and leaf-brass laid on the same. Then the air was 

 exhausted, when the glass ball was let down to about an inch, or somewhat 

 more, towards the pieces of leaf-brass : many of them were attracted by it. 

 Then the air was let into the receiver, and the leaf-brass laid on the stand, the 

 ball being as before suspended, was let down to about the same distance from 

 the leaf-brass as before, and there seemed to be very little difference in the 

 attraction. 



He has made the same experiments with sulphur, sheil-lac, rosin, and white 

 bees-wax. These would be attracted to the height of an inch and a half by 

 estimation ; and when the experiment was made with the receiver full of air, 



