118 WRITINGS OF JAMES SMITHSON. 



surfaces of them may be in the same plane ; and their dis- 

 tance is such that the needle when laid across them rests on 

 them at a small distance from the sides of the beam. They 

 rise above the surface of the table only one and a half or 

 two-tenths of an inch, so that the beam is very limited in 

 its play. 



The weights I use are one globule of gold, which weighs 

 one grain ; and two or three others which weigh one-tenth 

 of a grain each ; and also a number of small rings of line 

 brass wire made in the manner first mentioned by Mr. 

 Lewis, by appending a weight to the wire, and coiling it 

 with the tension of that weight round a thicker brass wire 

 in a close spiral, after which the extremity of the spiral 

 being tied hard with waxed thread, I put the covered wire 

 in a vice, and applying a sharp knife which is struck with 

 a hammer, I cut through a great number of the coils at one 

 stroke, and find them as exactly equal to one another as can 

 be desired. Those I use happen to be the l-30th part of a 

 grain each, or 300 of them weigh 10 grains ; but 1 have 

 others much lighter. 



You will perceive that by means of these weights placed 

 on dift'erent parts of the beam, I can learn the weight of 

 any little mass from one grain or a little more to the T2W 

 of a grain. For if the thing to be weighed weighs one 

 grain, it will, when placed on one extremity of the beam, 

 counterpoise the large gold weight at the other extremity. 

 If it weighs half a grain, it will counterpoise the heavy gold 

 weight placed at 5. If it weigh -jSg. of a grain, you must 

 place the heavy gold weight at 5, and one of the lighter 

 ones at the extremity to counterpoise it ; and if it weighs 

 only 1, or 2, or 3, or 4-lOOths of a grain, it will be counter- 

 poised by one of the small gold weights placed at the first, 

 or second, or third, or fourth division. If on the contrary 

 it weigh one grain and a fraction, it will be counterpoised 



