24 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



January, 



the i-artli till the month of its funnel (wliicli receives the rain) is on a level 

 with the ground surrounding it. Into this cylinder is put a float, with a 

 scale or graduated rod attached to it, which \\ill move up or down as the 

 water ri^cs or falls in the cylinder. There is a thin brass har fixed within 

 the funnel, about half an infli under its mouth, with an aperture in the 

 midille just large enough to .illow tlie scale so move easily through it. The 

 upper side of this cross bar is brought to a fine edge, so as to cut but not 

 obstruct the drops which may alight on it. There is an aperture also in the 

 bottom of the funnel, through which the water must pass into the cylinder, 

 and through which also the scale must move ; but this aperture requires to 

 be made no larger than just to permit the scale to move through it freely. 

 AVhen the gauge is firmly fixed, and the float and funnel in their places, 

 water is to be poured in till the zero of the scale is level with the upper edge 

 of the aperture. 



Mr. Tliom gave an account of the water filters used at Greenock and Pais- 

 ley. A species of trap rock or amygdaloid, common in the neighbourhood, 

 is broken to the size of small peas, and mixed with fine shaq) sand. The 

 ■water is filtered by passing directly downwards through the media, which 

 media are in their turn cleansed by passing the water through them upwards. 

 The filter does best at two feet of ])ressure and under. 

 " Description of a Itcroli-inij Balance." By Mr. Lothiau. 

 The opposing arms of this balance are curved, being formed of two spirals, 

 the one situated vertically over tlie other, and both bending round a common 

 centre of movement, which is jjlaced in the pale of the upper curve. The 

 spirals diverge from each other near their origin, but approach and merge to- 

 gether at tlieir extremes, and thus form one continuous curve, which is 

 grooved on its circumference. The cords or chains which suspend the re- 

 ceiving scale and counterpoise act against each other in this groove — the 

 weight of the scale, when hanging from a lengthened radiant of the upper 

 -piral, being in equilibrio with the greater weight of the counteq)oise when 

 hanging from a shorter radiant of the lower one. When this state of rest is 

 disturbed by loading the scale, the balance moves round, and, in the progress 

 of its revolution, the opposite eccentricities of the spirals combine in changing 

 the ratio of the leverage, and thus originate a self-adjusting power, by which 

 the loads of both cords arc mutually moved into equilibrium. The receiving 

 scale thus commences with greater, and ends w ith less mechanicel power than 

 the coimterpoise — a circumstance which is in harmony with the purpose of 

 employing an unchanging weight to measure others both less and greater 

 than itself ; while the principle is one which concentrates the power and 

 abridges the size of the machine. In order, however, that the total amount 

 of adjusting power thus generally obtained may be equally drawu upon and 

 advantageously distributed throughout the movement of the balance, a defi- 

 nite relation is established between the weight of the counterpoise and the 

 rates at which the accumulating weight of the scale and the leverage of the 

 lower spiral increase. The leverage of the upper spiral, being derived from 

 these ascertained conditions, is made to preserve a rate of decrease which 

 accords with the previously regulated increase in the leverage of the lower 

 curve ; while both spirals have their precise form determined by the additional 

 consideration of the direction in which the cords exert their power on the 

 chrcumfcrcnce of the balance. In their calculated formation, the two spirals 

 are thus dependent on and related to each other, while together they are 

 component parts of one continuous curve, in which the mutual and combined 

 changes of leverage are made to follow an equable, as well as a general pro- 

 gressive gradation ; by which means, the balance is moved through equal 

 angles by equal weights. In machines intended for weights of considerable 

 amount, the balance is made to revolve about an axis, which is itself sup- 

 ported, a little above its centre, on knife-edge rests, so as to combine the 

 movement of the revolving balance with the libration of the common one — 

 the coincidence of a pointer from the axis with the ordinary pointer of the 

 machine showing when the indication is practically unaffected by friction. In 

 machines for weights of still greater magnitude, the articles to be weighed 

 are made to act, in part, as their own counterjioise, by adopting differential 

 curves to diminish the descending power of the scale ; by which a compara- 

 tively small counterpoise is made to adjust the unsupported difference of 

 weights greatly exceeding itself. 



" On the Combmiion of Coal and the prevention of the generation of Smoke 

 in Furnaces:" liy Mr. SVilliams. 



Mr. Williams observed, that in treating on steam and the steam-engine, 

 the subject divides itself into the following heads : — 1st, The management of 

 fuel in the generation of heat ; 2nd, Tlie management of lieat in the genera- 

 tion of Kteam ; 3rd, Tlie management of steam in the generation oifuel. The 

 first belongs to i\\c furnace ; the second to the boiler; and the third to the 

 engine. The first, although exclusively in the department of chemistry, is to 

 be considered in the Mechanical Section, for the purpose of chowing its con- 

 nexion with the practical combustion of fuel in the furnace. The main con- 

 stituents of coal are carbon and bitumen : the former is convertible, in the 

 solid state, to the purpose of generating heat ; the latter, in the gaseous state 

 alone, and to this latter is referable all that assumes the character oi flame. 

 The greater part of the practicable economy in the use of coal being connect- 

 ed with the combustion of the gases, this division of the subject is peculiarly 

 important. We all know that combustible bodies cannot burn without air: 

 the actual part, however, which air has to act is little inquired into beyond 

 the laboratory ; yet on this part depends the whole of effective combustion. 

 Having explained the nature of combustion, Mr. Williams went on to show, 



that all depended on bringing the combustible and the air into contact in the 

 proper quantities, of the proper qualify, and at the projjer time — the proper 

 place, and the proper temperature. The conditions requiring attention were, 

 1st, The quantity ; 2nd, The quality of the air admitted ; 3rd, The effecting 

 their incorporation or diffusion ; 4th, The time required for the diffusion , 

 and, 5th, The place in the furnace where this should take place. Mr. WiUiams 

 euhibited several diagrams, representing the several processes connected with 

 the combustion of a single atom of coal-gas or carburetted hydrogen, and 

 also of bodies or masses of such gas. The essential rlifference between the 

 ordinary eouibustion of this gas in combination with atmospheric air, and 

 that resorted to by Mr. Gurney in combination with pure oxygen, in what is 

 called the Bude light, was then explained. By these diagrams, it was shown, 

 1st, What was the precise quantify of air which the combustion of gas de- 

 manded ; 2nd, The degree or kind of mixture which combustion required ; 

 and, 3rd, That the unavoidable want of time in the furnace to effect this de- 

 gree of diffusion was the main impediment to perfect combustion, and the 

 cause of the generation of smoke. From the consideration of these details, 

 the inference followed, that smoke once generated in the furnace cannot be 

 burned, — that, in fact, smoke thus once generated became a new fuel, de- 

 manding all the conditions of other fuels. Mr. Williams dwelt much on the 

 chemical error of supposing that smoke or gas can be consumed by bringing 

 it into contact or connexion witli a mass of incandescent fuel on the bars of 

 a furnace ; that, in fact, this imaginary point of incandescence, or the con- 

 tact with any combustible body at the temperature of incandescence, was 

 peculiarly to be avoided, instead of being, as hitherto, sought for ; and hence 

 the failure of all those efforts to prevent or consume smoke. The great evil, 

 then, of the present furnaces was their construction, which did not admit the 

 necessary extent of time (or its equivalent), time being essential to effect the 

 perfect diffusion of mixture of the gas, of which every chemist knew the im- 

 portance, and on which the experiments of Prof. Graham were so conclusive. 

 Mr. Williams then jirocceded to show", that unless some compensating power 

 or means be obtained, and practically and economically applied, we can never 

 arrive at full combustion, or prevent the formation of smoke. Tliis compen- 

 sating power was shown to be obtainable by means of surface, and was well 

 exemplified in the blow-pipe : the remedy then, for the want of time in the 

 furnaces, may be met, by introducing the air in the most effective situation, 

 by means of numerous small jets. Mr. Williams submitted the primary law 

 to be this ; viz., that no larger portions of air, that is, no greater number of 

 atoms of air, should he introduced info any one locality, than can he absorbed 

 and chemically combined with the atoms of the gas with which they respec- 

 tively come into contact. Again, that the effecting, by means of this ex- 

 tended surface, this necessary diffusion was the main condition which re- 

 quired attention, and not that of temperature. Jlr. Williams then exhibited 

 the diagram of a boiler to be constructed on the above principles, and stated 

 that he had an experimental boiler at work, which fully proved the accuracy 

 of the principle. 



Sir John Robisou stated, that the Committee of Recommendations had 

 suggested the appointment of a Committee to make a further investigation, 

 and report to the Association at their next meeting. — Mr. \ ignoles observed, 

 that the gradual increase of the aperture for the blast of cupolas for second 

 meltings of metal, the areas of which were now at least fifty times larger 

 than formerly, proved the necessity of admitting large quantities of oxygen 

 in combustion, which could only be obtained in its combination with the 

 nitrogen, the other component part of atmospheric air. 



" On the Temperature of tlie Earth in the deep Mines in the neighbourttood 

 of Manchester." By Mr. Eaton Hodgkinson. 



Mr. Hodgkinson having, some years ago, received from Prof. PhiUips four 

 thermometers belonging to the Association, got, thi-ough the kindness of the 

 proprietors of the following pits, and other parties connected with them, ex- 

 periments made upon the temperature of the earth in each of them : — The 

 salt-rock pit, 112 yards deep, belonging to the Marston Salt Company, near 

 Northwich, Cheshire ; the Haydock Colliery, 201 yards deep, near to War- 

 rington ; the Broad Oak Coal-mine, 329 yards deep, near to Oldham. In 

 the latter pit, a thermometer placed in a hole three feet deep, bored in 

 " metal," and closed at the aperture, was examined weekly by Mr. Swain for 

 twelve months, the temperature varying from 57^ to 581° Fahr. — it being 

 lowest from the beginning of February to the middle of May, and iiighest in 

 September and October to the middle of November. The experiments above 

 mentioned were made in 1S37 and 1838, and the results mentioned at the 

 Birmingham meeting ; but the Broad Oak pit having been increased in depth 

 since that time, a thermometer was inserted in it, in a hole bored in metal, 

 as before. It was in a place 408 yards deep, and indicated a temperature of 

 6F, remaining nearly constant for twelve months. Mr. Fitzgerald being re- 

 cently engaged in sinking a deep coal-pit at Pendleton, two miles from Man- 

 chester, Mr. Hodgkinson conceived this to be a favourable opportunity for 

 getting additional information on the subject of subterranean tempeiature, 

 and, on bis ai)plication to the proprietor, the engineer (Mr. Ray) readily 

 made for him, during the sinking of the pit, and afterwards in the workings, 

 the experiments of which the results are below. At 418 yards from the sur- 

 face, the temperature, in a hole from three to four feet deep, bored in dry 

 rock, was 06" ; at 450 yards deep it was 67°; and at 480 yards it was 69°. 

 In the workings at 461 and 471 yards deep, it was in both cases 05". The 

 mean temperature of the air at Manchester, according to Dr. Ualton's experi- 

 ments, is 48° Fahr. ; and, as the pits above mentioned are not very far from 

 Manchester, the mean temperature of the earth at the surface of each of 



