88 Balances for Delicate Weighing. [Jan. 



tested by pressing it upon a piece of wood to ascertain that 

 it neither bent, nor broke ; being afterwards examined by 

 the microscope. — The wire d, is the pointer, the point of it 

 being a continuation of the right line of the fulcrum and the 

 points of suspension for the scale pans. The end of this 

 wire entering the beam was hammered fiat, a slit was cut 

 down the end of the beam, and the wire thrust in and tied 

 securely with a piece of waxed silk thread as at g. 



6. The scale pans of this balance are supported in the 

 simplest manner I could devise. The crank piece e, fig. 3. 

 is a piece of common brass wire flattened on the top, hammer 

 hardened and polished underneath where it rests on the beam 

 point a. This crank piece has a hook or hole at the bottom 

 i. e.at f, and another piece of brass wire fig. 4. hooks on it, 

 the lov/er end of this wire fig. 4. being bent at right angles 

 into a triangular shape for the purpose of supporting the scale 

 pans, which are small thin dishes one inch in diameter. — 

 The ball over the fulcrum f, Fig. 2. is common to all the 

 balances, i. e. each balance has one ; it is for the purpose of 

 raising or lowering the centre of gravity, and the wire g, is 

 for the purpose of adjusting the equilibrium of the balance 

 before it is used. 



7. The sensibility of this balance is very great, in fact so 

 much so, that it is extremely difficult and tiresome to w^eigh 

 with it. Vvhen 20 grains are in each scale the odth part 

 of a grain occasions the pointer to move over 3 divisions of 

 the index, which is graduated in lOths of an inch ; suppos- 

 ing with 20 grains in each scale the index points at nonius, 

 or nothing, the addition of YoWt^^th of a grain causes the 

 pointer to move over a space of -jo^ths of an inch, so that 

 the balance indicates decisively to -g-^oo P^^^ ^ grain 

 which causes the pointer to move over J a division or 



of an inch, a quantity quite large enough to produce an in- 

 dication that may be depended on. Tn fact half that quanti- 

 ty or Y2-%-o odth part of a grain may be estimated, but all 

 who know the difficulties of such minute weighing are avv^are 

 that such statements appear much finer and more scientific 

 on paper than they are to be depended on in practice. 



8. A balance like this must be used with the utmost possi- 

 ble care, not as I once saw a gentleman use an assay balance^ 



