304 Defcriptkn if a Support applkalh to Balances, 



priving it in any refpeft of its precifion, (hould afford a convenient means of raifing and 

 lowering it at pleafure. It is well known bow troublefome it is to weigh by balances held 

 in the hand, and this trouble is' freqijently by no means the fmalleft inconvenience attend- 

 ing that method. 



Several artifts have invented fupports, convenient in their ufe, and ingenious in their 

 contrivance ; but each of thefe is adapted only to a fingle balance, and increafes the price 

 in ifuch a manner as to put it out of the convenience of moft phiiofophers and artiils. I 

 hope I fhali therefore give them pleafure by publifhing, in confequence of the invitation of 

 feveral celebrated chemifts, the defcription of a fupport, which, to the advantage of being 

 univerfal, adds thatof cheapnefs and eafy execution, whether in wood or in metal. 



It was my intention to have added to this defcription fome views refpeiling the theory 

 and con(lru6lion of balances, from which I apprehend that artifts acquainted with the 

 elements of geography and calculation might derive fome advantage in the improvement of 

 jnachipes for weighing; but as this part of my work is more extended than I at firft 

 thought, I (hall pubiifli it feparately. 



A triangular footof brafs, A. a-, a, «„ (Plate XVI, Fig. i & 2) has its three extremities, 

 a, a.' a'", folidly fcrewed to a table or horizontal plane. In the part A of this foot is 

 fcrewed a cylindrical ftem A B, of any convenient length. It may be proper to have two 

 of different lengths, in order to- exchange them when very large balances are ufed. Thofe 

 which I have ufed are of half a metre and a metre in length. ■ 



• A vertical pulley is placed at the top of the rod A B, fo that the fame vertical plane 

 paffes through the axis of the beam and the horizontal axis of the pulley. The fupport 

 C D of this pulley has at its lower part a cylindrical bore, into which the upper extremity 

 of the rod A B enters with an eafy friftion ; and a thumb-fcrew E ferves by its preiJure to 

 keep the pulley in its fixed pofition. 



Another pulley P is fixed below the rod A B, fo that the tangent line to the pullies P/ 

 is parallel to the axis of the rod A B. , i 



A ftring K ^/) H G P F, at the end of which is fu(pended; beyond" the edge of the table 

 K, a fmall weight, k pafles through a hole /, made in the foot a", thence over the pullies 

 p and P, and is faftened at F to the upper part of a piece m tn n q, which is forked, and to 

 tvhich are fufpended, as I fhall proceed to explain, the balance, the weights, and the 

 obje£ls to be weighed. F w is a button, which, being fcrewed to the top of the fork, re- 

 ceives the ftring through a hole, in which it remains by virtue of a knot made in- its 

 extremity. 



The tail, or lower pairt. of this fork, is prifmatic in its part m n; and this prifmatic part 

 enters into a notch// made in the extremity N of the horizontal piece N O, in which it 

 can freely Aide upwards and downwards through a limited fpace, its afccnt being ftoppe.d 

 by the enlargement of the fork below, and above by the' enlargement occafioned by the 



reparation of the two branches of the fork. 



4 The 



