November 2, 1893] 



NA TURE 



'9 



in the highest manner, and with mathematical accuracy. In 

 order to accomplish this a good light is necessary, but unfortu- 

 nately that is a thing Mr. Dobson can seldom get frooi natural 

 sources at his works. We do not as a rule expect to find 

 engineers and manufacturers exclaiming against the smoke 

 nuisance ; we rather look to hear such things from those who 

 cultivate the gentler arts. It is therefore, perhaps, worth while 

 to quote a few passages from Mr. Dobson's paper, in which he 

 speaks of the state of the atmosphere in Lancashire : — 



" Although Lancashire coal has a number of excellent quali- 

 ties, yet it is one that makes the most smoke of any. A large 

 portion of the Lancashire manufacturing industries, great and 

 •small, date from a number of years back, when smoke- 

 consuming and smoke-preventing apparatus had not yet been 

 <ievised ; and many of the factories are working at the present 

 <lay under pretty much the same conditions as when they 

 started. Hence the atmosphere in all manufacturing towns 

 in Lancashire is heavily charged with unconsumed carbon, 

 producing an excess of cloud and fog, which, while inducing 

 an excess of rain, acts also as a screen against the rays of the 

 sun, and thus does a double injury to the neighbouring agri- 

 -culturist, the producer of the country's native wealth. A circle 

 ■of thirty miles radius around Manchester is said to include a 

 larger population than an equal circle around any other place 

 in the world ; and within this circle, about twelve miles north- 

 west of Manchester, lies Bolton, the town with which the author 

 is best acquainted, where all winds, except the west and north- 

 west, bring the surcharged atmosphere from other manufactur- 

 ing districts, producing at any season of the year, if the wind 

 happens to be slight, a sky ranging from dull lead to dark 

 brown. For four years in succession it has occurred at the 

 writer's works, that on June 21, the longest day, the gas in 

 ever)' room, amounting to nearly 7500 jets, has had to be lighted 

 by eleven o'clock in the morning, and has remained lighted 

 until work ceased ; and this has occurred also in other towns, in 

 weather that ought to have secured abundant sunshine. To 

 such an extent does gloom prevail that in clear weather the 

 effect of bright sunlight becomes even distressing to the eye- 

 sight, simply from the rarity of the contrast." 



In endeavouring to improve the lighting of his shops, Mr. 

 Dobson naturally turned to electricity. Incandescent lamps 

 were tried, but these were not a very great improvement in 

 illuminating power over gas ; whilst with the arc lamp the 

 shadows were so hard and strongly defined that the workmen 

 preferred a very much weaker illumination, if more diffused. 

 When travelling on the Continent, Mr. Dobson visited some 

 cotton mills, and here he found what seemed a very perfect 

 system of illumination. Arc lamps were used, but they were 

 placed in an inverted position to that which is usual, the 

 negative carbon being above, and the positive carbon below. 

 This, of course, threw the greater part of the light rays up- 

 wards, as most of the illuminating power proceeds from the 

 crater of the positive carbon. The ceiling is kept well white- 

 washed, so that the light thrown up is again reflected down- 

 wards. The sides of the rooms are also whitewashed, in order that 

 a reflection may come from them. The result is that, with- 

 out any definite source of illumination being observable, the 

 whole room is flooded with a well-diffused light. Mr. Dobson 

 had very kindly arranged to have one of these lamps in the large 

 -visitors' room of the Institution of Civil Engineers, so that 

 ■members were able to judge of its efficiency for themselves. 

 The result was very perfect in regard to absence of shadows. 

 One could stand in any part of the room, facing any way, and 

 <read a book or paper without any very perceptible shadow being 

 thrown ; indeed, the diffusion of light appeared to us as good 

 as in the open air. Such a result is of the greatest importance, 

 and it is to be hoped that libraries and readingrooms especially 

 will in future largely adopt this system; or at any rate, that it 

 will be introduced to the exclusion of the direct arc lighting, 

 like that adopted with such unpleasant results in the reading- 

 room of the British Museum. In regard to the cost, Mr. Dobson 

 cannot speak positively on the subject, not having yet sufficient 

 data to go upon, but he anticipates that it will be higher than 

 •gas at Zs. 8d. per thousand, which is the price in Bolton. There 

 will, however, be a much larger volume of light than when the 

 gas was used, and the advantages of the system, in his opinion, 

 ' altogether outweigh any possible additional cost. In the dis- 

 cussion which followed, Mr. A. P. Trotter gave a good popular 

 explanation of the advantages of a dead white surface for reflect- 

 . ing light, as compared to that of a looking-glass or bright 



NO. 1 253, VOL. 49I 



surface. Good white blotting-paper, he saiil, reflects back 82 

 per cent, of the light ca'jt upon it. Many jiersons are under the 

 impression that looking-glass must be a Ijetter reflector than 

 paper or a whitewashed surface, because, with looking-glass, a 

 strong shadow can be cast, while from a dead surface no heavy 

 shadow is obtained. The reason, of course, is not so much that 

 the reflected light is less from the dead surface, but that the 

 reflection is concentrated in the case of the looking-glass ; with 

 paper or whitewash it proceeds from a vast number of 

 points. 



A modification of this system of reflected light, which is of 

 interest, has been adopted by Mr. A^pinall, the chief engineer 

 of the Lancashire and Yorkshire Railway, at the Horwich shops, 

 where the rolling-stock for the line is produced. In these shops 

 the roof is not adapted for putting in large whitewashed re- 

 flectors above the lamps, the jibs of travelling cranes, belting, 

 shafting, &c., being in the way; but Mr. Aspinall, having seen 

 the very perfect illumination obtained by Mr. Dobson at Bolton, 

 determined to see if he could not obtain a modified result. He 

 therefore inverted his arc lamps so as to get the positive carbon 

 below, as in the case of the Bolton installation, and the major 

 part of the light would be thrown towards the ceiling. Above 

 the lamp, and therefore not shielding it from view, was a white- 

 washed screen of boards, acting as a reflector. The effect was 

 far superior to that of the ordinary method of arc lighting, where 

 the dazzling stream of light pours upon the spectator to the de- 

 rangement of his eyesight, and at the same time casting heavy 

 and impenetrable shadows. This arrangement, however, is in- 

 ferior to the complete system, as described by Mr. Dobson, but 

 may be taken as a very good substitute where, from local 

 causes, the entirely reflected principle cannot be adopted. 



Mr. Borodin's paper on Steam Pumps was read on the second 

 day of the meeting, and led to a fairly long discussion. The 

 author gives details of a number of pumps tested in order to 

 find their efficiency under ordinary working conditions. The 

 paper has a commercial rather than a scientific interest, to this 

 extent — that it shows the manufacturers how badly machinery 

 may work ; for instance, a pump manufactured by an Englisli 

 firm of very good repute only gave 2953 foot lbs. of work 

 done per lb. of steam, when pumping .ngamst a head of 33 ft. 

 and the steam pressure being 90 lbs. Supposing the trial con- 

 ditions to be properly observed — which there is no reason to 

 doubt they were in the present instance — such a result could only 

 be due to the pump being in extremely bad condition, owing to 

 neglect or ill-usage. It had been in use for a number of years. One 

 meets with the same thing — perhaps to a greater extent — in steam 

 engines where the fuel consumption of 30 or even 40 lbs. pec 

 one horse-power per hour has been recorded. Mr. Borodm's 

 paper is useful as supplying awful examples for pump users, 

 and at the same time it opens up the very wide question of the 

 value of trial trip efficiencies. To tnke another instance, that 

 of war ships, a very high speed may be obtained on trial with 

 picked coal, picked stokers, engines thoroughly overhauled, 

 and, in fact, every possible precaution taken to procure effici- 

 ency. Naval captains are apt to say, " We would like to know 

 what our ship will do under fair working conditions in action, 

 rather than what she may be made capable of by tuning her up 

 to concert pitch." That is a very good argument for the cap- 

 tains, but where are we to draw the line? It is impossible to 

 lay down what are the fair conditions of ordinary service for 

 any class of vessels — how bad the coal should be, how ineffi- 

 cient the stokers, how rough the weather. Our only course is 

 to get the highest possible result in every case, and then make 

 such allowance as experience, or common sense, would dictate. 

 The same thing may be said with regard to the pumping 

 machinery dealt with by the author. For instance, a pul- 

 someter referred to in the paper was stated to require S60 lbs. 

 of steam per hour for a certain duty ; whilst experiments made 

 by Prof. T. Hudson Beere, with a pulsometer in good order, 

 gave the pounds of steam required for a similar duty as I47'6. 

 Now, it will be obvious that if a contractor requires a con- 

 venient pump like the puhometer, and is prepared to pay some- 

 what for the suitability in the matter of economy, he need not 

 take S60 as his figure of merit, when I47"6 is the trial trip 

 efficiency, although he may undoubtedly have to make some 

 allowance upon the latter figure. 



The paper was favourably received by the meeting, and will 

 no doubt add to the attractiveness of the volume of Transactions 

 in which it will appear. 



The meeting concluded with the usual votes of thanks. 



