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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[December, 



been sufficiently attended to. He fully approved of those forms of valves in 

 which the area was divided into several openings ; the loading the valve pro- 

 portionally was also of importance. All the ring valves, among which he 

 would include that of Mr. Hosking, tended to diminish the concussion ; hut 

 however good they might appear theoretically, there were some practical ob- 

 jections against most of them ; for instance, Harvey and West's valve was 

 not applicable for mines, because, as the two lifting faces were connected, a 

 chip or any sand being interposed between either of them would cause con- 

 siderable leakage in both ; the ring valves were not liable to this objection, 

 and therefore were preferable for mines or situations where the water con- 

 tained any foreign substances. The old butterfly leather valve had been 

 much improved, and recently a modification of it had been introduced which 

 promised to be very effective. The area of the valve was divided into eight 

 compartments, each covered by a triangular flap of leather, hinged to the 

 circumference of the bucket, and all meeting in the centre on a raised apex. 

 By this arrangement nearly the whole area of the pump-valve was opened ; 

 the cost of construction was also diminished, because, instead of cutting the 

 large flaps only out of the finest and largest hides of leather, small pieces 

 could he used : valves thus constructed, had been in use in mines for upwards 

 of seven months, without repair. The improvements in the valves had pro- 

 duced a corresponding increase in the height of the column of the pumps: 

 it formerly was about 15 fathoms; Woolf had gradually increased it to 40 

 fathoms; and now a column of 50 fathoms was sometimes used, lie was 

 an advocate for giving a very large area to the suction-pipes; for instance, 

 in one mine under his direction, to a valve 20 inches in diameter, two 

 suction pipes, each of 20 inches diameter, hail been adapted, with great ad- 

 vantage to the engine ; the pump drew more water and worked much more 

 steadily. 



Mr. Parkes remarked, that the concussion arising from the closing of the 

 valves of low-lift pumps, was more destructive than in the high-lifts ; an en- 

 tirely different system was therefore pursued in pumping. The engine 

 started very rapidly, and was generally worked much faster, which altered 

 the condition of the pumping. At the engine of the Wahlersea drainage, 

 near Wisbeach, there was a pump of 6 feet diameter, with a length of stroke 

 of 8 feet, the valves were formerly destroyed more rapidly than in any mine 

 in Cornwall ; recently, Mr. Hosking, had adapted to it a larje box, having 

 in the centre a valve of 30 inches diameter, and around it five other valves, 

 the sum of the area of the six valves being greater than that of the pump : 

 the result was a great diminution of concussion, and consequent increased 

 durability of the valves. 



Mr. Glynn agreed with Mr. Taylor, in thinking that Messrs. Harvi \ and 

 West's valves, were not so well adapted for mining purposes as they were for 

 water-works, or for situations where only clean water was passed through 

 them. Mr. Darlington had introduced a modification of the valve, which be 

 thought would be very efficacious; it was being constructed by the Butterley 

 Iron Company, and he would send a description of it to the Institution. 

 This principle of large valves had been extended to blast engines; the size 

 of the air-valves having been much increased, a corresponding advantage had 

 been found in their duration, as well as in the work of the engine. 



June 27. — The President in the Chair. 



" On the present State of the Streets of the Metropolis, and the im- 

 portance of their amelioration." By Charles Cochrane, President of the 

 Association for the Promotion of Improved Street Paving, &.C. 



This paper first refers to a Commission formed by tic present Govern- 

 ment, " for inquiring into and considering the most effectual means of im- 

 proving the Metropolis, and of providing increased facilities of communica- 

 tion therein ;" also to a Report of a Committee of the House of Commons, 

 which recommends '• that an institution should be formed expressly for as- 

 certaining, by a succession of experiments, the best mode of constructing 

 roads and keeping them in repair." 



A brief history of the different kinds of carriage-ways and foot-pavements, 

 is then given, showing that the resources of art and science have been but 

 little consulted in their construction, which is illustrated by the system of 

 making macadamized roads, their formation being nearly dependent upon 

 the amount of traffic upon them. It is also stated that few, if any, im- 

 provements have been made in the method of forming granite pavements; 

 the system practised twenty years since being nearly the same as at present, 

 whicli is, to imbed the stones in the earth by means of mere manual strength, 

 although, of late years, the aid of grouting has been occasionally brought 

 into use. That in foot-pavements the same fault is perceptible, namely, the 

 want of a good foundation, as the masons generally seem to think, that so 

 long as the edges of the flags are well covered with mortar, and the work 

 when completed presents an uniform surface, the chief objects are accom- 

 plished. 



It is stated that wood paving, of which 100,000 yards have been laid down 

 in the metropolis, appears likely, from the successful trials which it has 

 undergone, to he generally adopted, the only objection against it being, that 

 it is slippery in wet weather ; this evil is chiefly attributed to the mud which 

 is brought from the other kinds of paving anil allowed to remain on it. In 

 all other respects, wood appears a superior material to any other hitherto 

 employed, for making roads, both as regards its general economy and du- 



rability, as well as its facility of traction, and more especially its extreme 

 cleanliness. 



The question of cleansing streets is then entered upon, when it is shown 

 that the oftener streets are cleansed, the less mud is created, whilst the at- 

 tendant expenses are not increased and the roads are kept iu better preser- 

 vation. From calculations made by the municipal authorities at Manchester, 

 on the relative advantages of machinery and manual labour, in cleansing the 

 streets, the results of which are given in a table, it is shown that the extent 

 of surface swept is the same, although not the extent of streets, arising from 

 the more or less frequency of sweeping over the same surface; so that by 

 cleansing the streets with Whitworth's street-sweeping machine, three times 

 a week, the quantity of mud produced on the surface is five times less, than 

 when they were swept by hand, twice in three weeks, and thirteen times less 

 than when swept but once a week. 



The losses caused by the dust and dirt in the streets are stated to be very 

 great ; Mr. Mivart, of Mivart's Hotel, estimates his actual loss at about £865 

 per annum, whilst shop-keepers in Oxford-street and Regent-street, state that 

 they lose annually from £30 to £300 per annum, by the destruction of their 

 goods bj the dust, &c. 



Some suggestions are given for improving, repairing, and cleansing the 

 streets, and it is stated that there are abundant means at present available, 

 for keeping them comparatively free from mud, if machinery was properly 

 employed. 



" On the relative merits of Granite and Wood Pavements and Macadam- 

 ized ltoads ; derived from actual experience." By D. T. Hope (Liverpool). 



In this communication the author alludes to the inefficiency of many of 

 our finest specimens of paving, arising from the desire of reducing the out- 

 lay, hut which, in teality, are executed and maintained at a great expendi- 

 ture, without securing the advantages which the material is capable of af- 

 fording, or the qualifications requisite for streets ; — and to the cleanliness, 

 comfort, and true economy, in having the work performed in the best man- 

 ner, and employing material best calculated for producing all those advan- 

 tages, which may he reasonably expected in streets of the present day. 



The following requisites that a good road or pavement ought, in some de- 

 gree, to possess, are laid down down as a standard, by which the respective 

 systems are compared; and a certain value (according to the experiments on 

 the several modes) attached to each, for the convenience of more obviously 

 contrasting their several qualities, viz. — 



1. A solid and compact structure, capable of resisting the effects of 

 traffic, without being cut up into ruts and inequalities from other causes 

 than mere abrasion. 



2. Not requiring to be frequently repaired. 



3. As much elasticity in the material, as may he useful in aiding the 

 power in draught. 



4. A firm and smooth surface, that the power employed may not require 

 to be ever vaying. 



5. Although comparatively smooth, to be free from slipperiness. 



6. To afford a sure foot-hold for the horse. 



7. Not liable to be seriously affected by the changes of the atmosphere, 

 or by repairs. 



8. An absence of mud and dust. 



9. A freedom from noise. 



10. To afford economy in transit. 



1 1. An economy in the construction and maintenance, consistent with the 

 preceding advantages. 



12. Not subject to rapid abrasion. 



It is shown that macadamizing has few, if any, advantages for public 

 thoroughfares — arising from its rapid abrasion, the frequent application of 

 new metal — the uncertainty of its condition, varying with every change of 

 weather — the abundance of mud and dust — and the great expence of main- 

 tenance ; and from the power employed in draught requiring to be so vari- 

 able, that the cost of transit is not only increased, but the horse is ofteu 

 compelled to exert more power at one time or in one part of the street, than 

 should ever he required of it. And also, that the advantages which may be 

 claimed for macadamizing in streets, are attainable in other descriptions of 

 paving, if proper attention be paid to their construction. 



