278 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



Three of the furnaces are blown with air, heated to about 680° Fahren- 

 heit. 



The engine has a blowing cylinder of 80 inches diameter, with 8-feet 

 stroke, discharging 558 cubic feet of atmospheric air at each stroke, under a 

 pressure of 3 lb. per square inch, or about 7800 cubic feet per minute ; the 

 diameters of the nozzles of the blast-pipes vary from 2$ to 3 inches, ac- 

 cording to circumstances. 



The principal dimensions of the furnaces are given, and the communica- 

 tion is illustrated by two drawings of the furnace and the barrow, in plan 

 and elevation, with details of construction. 



Automaton Balance for Weighing Coin. 



" Description of the Automaton Balance for weighing Coins, irwenied by 

 William. Cotton, Esq., Governor of the Dank of England." By Thomas 

 Oldham, Assoc. Inst. C. E. 



The paper first gives a brief notice of a portion of the bullion transactions 

 of the Bank of England, in order to explain the difficulties which led to the 

 invention of the machine. The new coinage first arrives at the Bank from 

 the 'lint in what are called "joumies," a single journey weighing 151b., 

 and containing 701 sovereigns. The officers of the Mint are allowed 12 

 grains plus in every pound-weight of metal, for the irregularities incidental 

 to working it into coin, but they usually work to within half that allowance, 

 wl::ch is technically called " the remedy." 



There have been coined for the Bank lately 8,000,000 of sovereigns, and 

 the greatest variation from the weight allowed was only 60 grains, or one- 

 Ihirf of the remedy : each sovereign should contain a portion of this remedy, 

 tn allow for wear in public use, and this extraordinary subdivision of the 

 j'.etal is invariably obtained. The usual delivery of new coinage at the Bank 

 contains 100 joumies, which is counted by weight only — that is, 200 snve- 

 r( igns are counted into one scale, and the rest of the delivery is weighed in 

 parcels which balance these 200, and this is all the counting the new coinage 

 receives. The regularity and precision of the manipulations at the Mint 

 obviate the necessity of any further examination, either at regards the gross 

 amount or the weight of an individual piece. 



When the currency returns to the Bank from the public it becomes neces- 

 sary to ascertain if it has been reduced below the standard weight, and this 

 imposes an arduous duty on the officers of the Bank. The amount of gold 

 paid daily over the Bank-counter varies considerably, but 30,000 may be 

 taken as a rough average, and hence arises a tedious, irksome, and expensive 

 process in weighing so large a number of pieces singly and in quick succes- 

 sion, separating, at the same time, the light from the standard coin. 



The mode of weighing coins by hand requires much dexterity, practice, 

 and attention ; but, in spite of all these, errors were inevitable, and it was 

 to obviate these that the machine was invented by Mr. Cotton, the Governor 

 of the Bank of England : it was constructed from his plans, by Mr. Napier, 

 (of York Road, Lambeth,) and is thus described : — Its exterior presents a 

 plain brass case, with a small hopper tube on the top plate, about 4J inches 

 from which there is an opening in the top plate. In this opening is seen a 

 platform in the form of a quadrant. This platform is suspended above one 

 end of the beam, and is to receive the coin to be weighed. On one side of 

 the case is a till — to receive the sovereigns as they are weighed— partitioned 

 so that one division is left for standard coin, and the other for such as are 

 light. There is a sliding door to each division, for removing the coins at 

 pleasure. The machine may be worked like a clock, with a weight, or by 

 any simple application of power. 



Its visible action is as follows : — The hopper being filled with gold, upon 

 setting the machine in motion, it immediately places a sovereign on the little 

 platfoim which serves, as already stated, in place of a scale-pan, and if it is 

 of standard weight, a small tongue comes rapidly forward and pushes the 

 sovereign into that side of the till allotted to such coin ; if light, another, 

 and similar tongue to the first, pushes the sovereign into the other side of 

 the till. The action of these tongues is at right angles to each other. 

 While a sovereign is being weighed, a succeeding one is on its way from the 

 hopper to the platform, and the moment the preceding sovereign is disposed 

 of, according to its value, another is placed in its stead. To keep the hopper 

 supplied with gold, and remove it from the till as it is filled, is all the at- 

 tendance necessary. 



The more minute parts of the mechanical arrangement of the machine, 

 such as the fulcrum, the forceps, &&, are described in detail, and the fol- 

 lowing statement by Mr. Miller is given, as a comparison with the old 

 method of weighing : — " With the bullion-scales 4000 may be stated as the 

 number a person can weigh in six hours. As the sovereigns now tendered 

 at the Bank-counter are most of them new, the scale dips quickly in weigh- 

 ing, and one person can weigh 5000 in six hours ; but a short time ago, 

 before the issue of the new coinage, the same person could only weigh 3000, 

 as it took a longer time for the scales to indicate. The bullion-scales cannot 

 indicate nearer than -j-^ths of a grain at the above rate. The machine is 

 perfectly free from the sources of error to which the scales are subject, and 

 weighs as quickly, whether sovereigns are new and of full weight, or old and 

 doubtful; it can weigh 10,000 in six hours, and divide coin varying only 

 ^th of a grain." 



The paper is illustrated by two drawings of the internal arrangement of 

 the machine, and a model showing the action of the tongues and platform. 



Remarks. — Mr. Oldham exhibited the automaton balance at work weighing 

 coin ; and after describing, with the aid of a diagram and model, the action 

 of some of the more delicate parts of the machine, he observed that in 

 seeking to obtain extraordinary performances by machinery, mechanical pro- 

 priety of construction was too often overlooked, and premature deterioration 

 in the action of many parts was the result. The automaton balance was 

 peculiarly worthy of notice from the judgment exercised in its relative pro- 

 portions, as was proved by the fact that, after being at work for several 

 months, it had become more delicate in detecting slight variations between 

 standard and light coin than when it was first constructed. Mr. Cotton's 

 object in this invention should be well understood. Public convenience de- 

 manded great accuracy in weighing the currency; by the ordinary mode of 

 weighing gold with the bullion scales — although it was due to the bank- 

 tellers to state, that they gave the utmost attention to their monotonous 

 duty — it was nearly impossible to guard against the various difficulties de- 

 tailed in the paper.' The injury sustained by the optic nerve, from constantly 

 watching the indicator of the scales, was a serious inconvenience to the ope- 

 rative, which, coupled with the incidental sources of error referred to, cre- 

 ated even greater absence of delicacy than the paper stated. Errors to the 

 amount of one-third or even half a grain were not unfrequent. By the 

 " automaton balance," the number weighed in a given time was increased, 

 and undeviating accuracy obtained. The delicacy of the instrument was 

 such, that from 30 to 35 coins per minute could be passed through the 

 machine, detecting a difference of only ^ of a grain. It should be men- 

 tioned that much greater delicacy could be accomplished, that is, to the 

 7 kydth of a grain, but not at the same rate ; because it would be understood 

 that a slow action of the beam was necessary for very small variations, and 

 that must regulate the speed of working ; but such delicacy was beyond all 

 useful purposes in those transactions which it was intended to improve. 



Mr. Cotton said that his attention had been attracted to the point by the 

 inconveniences to which the "tellers" were subjected in weighing gold for 

 the public : with balances so delicately constructed as the bullion scales, the 

 agitation of the air by the sudden opening of a door, or even by the breath- 

 ing of those around, sufficed to cause errors. It was possible, also, by pres- 

 sing the fulcrum against the bridle, to produce such a degree of friction as 

 materially to interfere with accuracy ; and the tellers confessed, that after 

 weighing two or three thousacd coins the sight was injured, and they no 

 longer observed with the same degree of correctness. He therefore ima- 

 gined that a machine might be contrived, which being defended from ex- 

 ternal influence, might weigh coins as fast as by hand, and within one-fourth 

 of a grain; but he certainly did not contemplate attaining such perfection 

 as the machine now possessed. His first idea was, that the light coins 

 should be taken off" by a forceps, and that those of average weight should be 

 pushed off by the succeeding ones ; but it was found, that the slightest in- 

 accuracy in the milled edges sufficed to give them a wrong direction : there- 

 fore, when he made the first rough sketch, and consulted with his friend, 

 the late Mr. Ewart, he recommended that Mr. Napier, of York Road, Lam- 

 beth, should be employed to make the machine, and to him was due the 

 sugeestion of the two alternately advancing tongues, as well as several other 

 arrangements of the machinery,' which he had so successfully constructed. 

 When the first machine was tried, out of 1000 sovereigns, 160 were found 

 to be light. Thev were given to a teller to be verified, and he returned 

 several of them as being of the proper weight ; but upon again weighing 

 them more carefully, the result given by the machine was found to be correct. 

 As an instance of how many circumstances should be taken into consideration 

 in delicate machines, he might mention that, after being used for a time, the 

 machine varied in its results, and on examination it was discovered that the 



