304 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[October, 



))osinof the necessity of Iiavinf? the vaulting, as well as all the 

 liintier wm-k in the lower ]iart of the church, entirely and care- 

 fully rciMiiveil. Xew and tliicker vjiultiiiy was then substituted f(ir 

 that which wiis taken down, and the whole of the floor over it was 

 laid with Yorkshire and Shannon flan;s set in Roman cement. New 

 ]iews were erected, restinj^ on iron chairs let into the flag-ffinfr; the 

 flooring of all tlie jiews was constructed so as to be occasionally 

 removed for inspection; Roman cement was internally used next 

 to, and at the bottom of the walls; and iron columns were substi- 

 tuted for those of tind)er in the lower tier. 



Here I must notice the clever plan of my friend, Richard 

 ]$eamish, Esq., C.E., who caused a screw to be placed in the head 

 of each iron column, which was screwed up so as to take the load 

 I)efore the temporary supjjorts were removed, thereby avoiding the 

 fracture consecpient on m-dinary wedging, so that all was effected 

 witlioiit any disturbance or sinking of the galleries, and the 

 columns wliich supported the roof, &c., the screws in each column 

 being accurately adjusted so as to meet the i)ressure from above. 



The expense incurred by these i-epairs was very considerable; 

 but it is satisfactory to state, that there has not been a re- 

 appearance of the dry rot since that time, now a period of sixteen 

 years. 



BRITISH ASSOCIATION. 



Nineteenth 3Iecti)ig, — held at Binninc/hiim, September, 1849. 



{From our own Correspondent.) 



Mechanical Section. 



President — fi. Stephenson, Esq. M.P. F.R.S. 



Vice-Presidents— Uesivs. W.Blake, W.Fairbairn, F.Osler, T. Webster. 



Secretaries — Messrs. \V. P. Marshall, C. Mandy. 

 Committee— y[ti%v%. J. G. Appolrt, W. Baker, R. Ddvison, C. Fox, J. Hender- 

 son, E. Hodgkinson, Rev. S. King, Messrs. J. G. M'Cunnell, R. Martineau, 

 G. Nasiiiyth, R. S. Newall, R.Roberts, J.Taylor, F. Whishaw. 



1. On n Method of Supplying the Boilers of Steam-Ennines with 

 Water. By Mr. \V. S. M'ar'd. 



Mr. \Fard proposes to use a small supplementary pumping en- 

 gine, having a working cylinder with valves so arranged that the 

 ])iston may be put in motion by either steam or water passing 

 through it, to be supplied with 'steam, by a steam-pipe, the en- 

 trance to which is somewhat narrow, and inserted in the boiler to 

 he sujiplied a little above the level at which it is desired to main- 

 tain the water therein. Such aperture should also be about the 

 centre of a marine boiler. The working cylinder should be at- 

 tached to a pump of sucli size as to be easily worked by the pres- 

 sure of the steam. The exit-pipe of the steam-cylinder must 

 communicate with tlie inlet-pipe of the pump, so that if the cylin- 

 der be actuated by steam, the steam will be condensed, and its 

 heat communicated to the water to be supplied to the boiler; or if 

 the working cylinder be worked by water proceeding from the 

 boiler, a considerable part of such liot water will be returned by 

 the pump. The mode of operation of such apparatus will be, that 

 whenever there is a working pressure of steam in the boiler, the 

 apparatus will be in action; but if the level of the water be below 

 the aperture of the small steam-pipe, the action will be moderately 

 rajiid, and a supply of water be pumped into the boiler; and when 

 the water in the boiler rises to the aperture, this being small, will 

 be as though choked by the water, which will be forced through 

 the working cylinder, moving-the ])iston and pump very slowly; a 

 l)ortion of the water thus escajjing from the boiler will be returned 

 by the pump. Such last-mentioned action cannot continue long, 

 inasmuch as the level of the water must be reduced; therefore the 

 average level of the water in the boiler will be, with slight oscilla- 

 tions, maintained at the height of the sui)plyiiipe. 



Remarks. — Mr. Roberts slated that the priMciple had heeji applied more 

 than thirty years, and he considered that many plans in ute, especially that 

 wherehy the principle of gravity was made available, was sufficient for the 

 purposf. 



I lie President observed that at a certain point the pipe leading to the 

 cylinder «ould adndt water mixed with tlie steam. This was an insuperahle 

 ohjection, inasmuch as tlie admission of such a mixture into the working 

 ))aits of an engine led to breakage. When the water got between the clack 

 and the hucket it was almost inipossihle to work the pump. This was mani- 

 tebt in the difficulty experienced in supplying locomotives. In some of the 

 eailier engines it was customary to fill the boilers as full as tlicy could hold, 

 run them as long as possible, and stop to take in a new supply of hot nater 

 directly into the boiler. His father, the late George Stephenson, obviated 

 this difficulty by introducing a cock between the bucket and clack, which, 



from its office of humouring the action of the machinery, was called the 

 "pet tap." He was afraid that the suggestiou of Mr. Ward was not practi- 

 cally useful. 



3. On a Chain Pipe far Sub-Aqueous Telegraphs. By Mr. F. 

 Whisiiaw. 



Tlie pipe is formed of iron tubing in lengths of from 1 to 3 feet, 

 and from 1 to 2i inches diameter, and connected together by ball- 

 and-socket joints; the length of the link is regulated according 

 to the sinuosity of the river. The joints are not made water- 

 tij^ht, it being unnecessary, as the pipes form a jacket only to the 

 wires, which are protected by a coating of gutta percha. The 

 tubes are pinned down to the bed of the river, and are merely used 

 as a protection to prevent abrasion of the wires. A similar chain 

 has been in use for some time in conveying the wires across the 

 rivers of Prussia and Germany: the longest length is 1,200 feet, 

 for conveying the wires of the electric telegraph across the Rhine. 



3. On Correct Sizing of Toothed Wheels and Pinions. By Mr. 

 Richard Roberts, of Manchester. 



Although much has been written on this subject, and on the best 

 form of teeth, there is still mucli difference of opinion on both points; 

 which difference is not confined to individuals, as it embraces the 

 members of the trade or profession to which they belong. For 

 instance, engineers, millwrights, and machinists in general, adopt 

 the plan of extending the teeth of the pinion and wheel to the 

 same distance beyond the pitch-line. A majority of them are 

 agreed as to the best form of teeth — namely, the cycloid for wheels 

 to work in straight racks, and the epicycloid for wheels to work 

 in other wheels, or in jjinions. But they are not so well agreed 

 respecting the length of the teeth, as the makers of watches, 

 clocks, and chronometers do not extend the teeth of the pinion 

 beyond the pitch-line more than one-half as far as they do the 

 teeth of the wheel; hence the preference given by those trades to 

 the "bay-leaf" form for the teeth of the pinion, as no other form 

 would pitch, with their sizing. 



Mr. Roberts obser\'es that various rules are given in works on 

 horology for sizing wheels and pinions, but he believes "movement 

 makers" generally, English and foreign, use an instrument called 

 a "sector" (resembling a "two-feet rule"), which is divided into 

 equal parts throughout its length, commencing about half a division 

 from the centre of the joint. The numbers up to 10, or 12, on the 

 sector are usually subdivided, for the use of artists «ho may 

 prefer pinions a little larger than the corresponding number on 

 the sector would give. 



Knowing it to be essential to the correct performance of any 

 machine where wheels and pinions are employed that they should 

 be properly sized, Mr. Roberts thought it might be useful to 

 parties whose experience on the subject has been more limited 

 than his own, of whom there might possibly be some present, to be 

 informed respecting the plan which he has adopted for more than 

 30 years for sizing toothed wheels. — With this object in view, he 

 has constructed an instrument which represents on a large scale 

 the sector used by clock and watch makei's; excepting that in their 

 sector the divisions are marked on the inner side of the limbs, 

 whilst in his sector the divisions commence at the centre of the 

 joint, and are continued in a straight line to within about |-inch 

 of the outer side of the limbs at the other extremity. 



It has long been the practise in Manchester to make those 

 wheels which come under the denoiuination of "clock-work," with 

 some definite number of teeth to the inch diameter, taken at the 

 pitch-line, and to distinguish the pitch accordingly. Mr. Roberts 

 has done this, and has adopted the same plan in respect to mill- 

 gear; substituting the foot for the inch in designating the pitch, 

 instead of naming it by the distance from the centre of one tooth 

 to the centre of the next, which is, he believes the universal 

 practice. 



Before explaining the way in which his instrument is used, he 

 mentioned that in the year 181 6, he had a set of change-wheels 

 made by a "factory clockmaker," which wheels were so much out 

 of pitch as to direct his attention to the cause of the defect; and 

 having found that the error bad arisen from the defective principle 

 of the sector, he immediately contrived his sector, which differs 

 from the clockmakers' sector principally in the joint being ad- 

 justable like that of the projiortionable compasses. The use of 

 this kind of joint was to enable parties to pitch wheels correctly, 

 and to suit themselves as to tlie depth of the teeth. 



After he had sold a number of sectors of this kind, he found 

 that, for all ordinary pur])oses, a fixed joint would answer equally 

 well, provided the centre of the joint was equal to two of the 

 divisions of the sector below zero. This circumstance led him 

 to make sectors (bars of brass serrated on the edge) which are 

 cheaper, whilst they are better suited for the workshop. 



