August 9, 1894] 



NA TURE 



365 



Cfrtr\in -ither stars, it is thought that these bodies must be at a 

 lumpeiature higher than that of the most powerful electric spark, 

 for. were they at this temperature, laboratory observations 

 intlioate that the group should be well visible in their spectra. 



The August Swarm of Meteors. — Many have already 

 begun to observe, during the past few evening-, some of the fore- 

 runners of the August swarm of meteors which at this time are 

 visible in very considerable numbers. Although, at its best, 

 this swarm does not offer such beauiiful displays as those 

 which occur when the earth meets with the densest part of 

 the November swarm, yet, on account of their uniform distri- 

 bution and moderate density along their orbit, the shower is 

 always fairly bright ami distinct. Unlike the November meteors, 

 the Perseids always herald their approach a few days before- 

 'band by an increasing number of outliers a? the maximum ap- 

 proaches ; on the loth this is reached, and from that time 

 a decrease in their number rapidly diminishes. Another pecu- 

 liarity of this swarm is that the average intensity year by year 

 does not exhibit such wide variations as those shown by the 

 Leonids, which attain a maximum evepy33i years. By plotting 

 the paths of the observed meteors on a globe or star chart, the 

 radiant point so found should be approximately 45° R. .\. and 57° 

 Declination for the loth. Close observation every evening wdl 

 -reveal a daily movement of the radiant point eastward among 

 the stars, as shown in tlie following ephemeris, taken from Mr. 

 Denning's table in the "Companion to the Observatory." The 

 dates before the loth are given for the sake of those who have 

 •commenced their observations early, and would like to compare 

 4heir observed radiant points with those calculated : — 



"The comet with which these Perseids are supposed to be con- 

 nected, is that which appeared in 1862, and was discovered by 

 Mr. Swift, of Rochester, .Vew Vork, on July 15. The orbit, 

 after a calculation m.ade by the late Dr. Oppolzer, of Vienna, 

 was found to be elliptic, and the periodic time 120 years. 

 Schiaparelli it was, however, that drew attention to the simi- 

 larity between the meteoritic and cometary orbits. The next 

 appearance of the comet ilues not t.ike place before another half- 

 century. 



INSTITUTION OF MECHANICAL 

 ENGINEERS. 



"TPIIE annual summer meeting of the Institution of Mechanical 

 Engineers was held last week in Manchester, under the 

 presidency of Prof. .\. B. \V. Kennedy, the President of the In- 

 stitution. The meeting commenced on Tuesday, the 31st ult. , and 

 concluded on the Friday following. There were but two sittings 

 for the reading and discussion of papers. The following is a list 

 of the papers on the agenda : — 



(1) " Desciiption of the New Electric Lighting Works, Man- 

 chester," by Dr. John Hopkinson, F.R.S. 



(2) " Electric Welding," by Benjamin /Vlfred Dobson. 



(3) " Description of Twin .Screw- Propellers with ..Vdjustable 

 Inimersion, fitted on Canal Boats," by Henry Barcroft, of 

 ^|-•^vry. 



U) " Description of the Manchester Main Drainage Works," 

 by Wm. Thomas Olive, Resident Engineer. 



(5) " The Manufacture of Standard Screws for Machine-made 

 Watches," by Charles J. Hewitt, of Prescot . 



(6) " Drilling Machines for Cylindrical Boiler Shells," by 

 Samuel Dixon, of Manchester. 



The last two papers were adjourned until the next meeting 

 in London. Dr. Hopkinson's paper was a short one, the scope 



NO. 1293, VOL. 50] 



of which is sufficiently indicated by the title. Outlined par- 

 ticulars were given of the new installation at Manchester. There 

 were, however, no special features which require notice in the 

 present instance. The discussion which followed chiefly turned 

 on the use of jockey pulleys. It is interesting to notice, how- 

 ever, the progress that has been made in electric lighting since 

 the author read his first paper on the subject before the Institu- 

 tion, now fifteen years ago. Since that time this department of 

 practical science has undergone an extraordinary development. 

 The only electiic lights then were arc lights, the first incan- 

 descent lights in a practical form being made about a year later. 

 To-day there are millions of incandescent lights in use. The 

 machine the author used for experimenting upon in 1879 was 

 at that time cofisidered a fairly large one and highly economical ; 

 it required si.x horse-power to drive it. Now many machines 

 have been working for a considerable time, requirinij over 

 1000 hor>e-power to drive them. The commercial efficiency 

 of the machine then was about 50 per cent., but now machines 

 are produced having commercial efficiencies of 94 per cent. 



Mr. Dobson's paper on electric welding was one of practical 

 interest, although the system of welding by electricity is one 

 that is now well known. The author, has, however, adopted this 

 method of joining metal for some time in the extensive works of 

 his firm at Bolton. Practical every-day working for nearly three 

 years of the process of welding by electric force enabled him to 

 give certain indications and appreciations of the method con- 

 sidered as a practical workshop operation. During the period 

 mentioned his firm has had two machines in operation, worked 

 from the same generating dynamo, and engaged upon different 

 classes of work. The one is specially arranged for joining bar 

 iron and steel, and the other, which is a smaller machine, is 

 used for work of a more delicate nature, such as brazing and 

 piecing clean-finished work, where the fire-heat would have de- 

 stroyed the quality of the work on the adjacent material. Great 

 difficulties were experienced at first in regard to the requisite 

 mechanical power, it being found that this power had been 

 much understated. The author, having about 35 indicated 

 horse-power to spare on a certain engine, and understanding 

 that 30 horse-power would be the utmost required 10 piece a 

 2-inch round bar, determined to drive the dynamo from that 

 engine. This practical test showed that instead of 30 horse- 

 power as much as So horse-power seemed to be wanteil for the 

 larger sizes. A portable engine capable of working up to too 

 indicated horse-power with So lbs. pressure was supplied and 

 placed at a distance of about 45 yards from the welding machine. 

 Even with this engine it was tound that when piecing the larger 

 diameters — as yet nothing over 2j inches has been pieced — if 

 the work was to be done in reasonable time, the speed of the 

 engine was greatly checked. A Thomson- Houston welding 

 dynamo was used by the author's firm. Its speed is 1000 re- 

 volutions per minute, and it gives at full load a current of 200 

 amperes at 300 volts with 100 alternations per second. Trans- 

 formers are used. The author gave full particulars of the work 

 done and tests made. The question of cost had not been 

 alluded to in detail by the author, who admitted, however, that 

 the payment of royalty, the cost of horse-power, and 

 the depreciation, which on electrical apparatus is heavy, 

 together brought the cost considerably over the net cost 

 of the ordinary smith's hearth work ; the payment in 

 wages, &c. , being considerably less. The loss in weight 

 of iron is about one-twentieth. On straightforward welds the 

 total cost is between ten and fifteen per cent, more than 

 the ordinary smith's work ; but in the case of delicate work and 

 difficult operations, the cost is about one-third of th.at of the 

 smith's work. The real advantage of the apparatus, as at 

 present arranged, is not so much an economy as a method of 

 securing an absolutely reliable result, and occasionally saving 

 considerable expenditure by its adaptability. 



In the discussion which followed the reading of this paper, no 

 important points were brought forward. 



Mr. Barcroft in his paper described an arrangement by 

 which steam power could be applied to ordinary canal boats. 

 Although doubtless the application was suitable lor the position 

 it had to fill, the machinery possessed neither scientific nor 

 engineering interest, except of a very limited order. 



.Mr. Olive's paper on the Manchester Main Drainage Works 

 was a ustful description of an ordinary installation of this 

 nature. The Manchester works have but recently been put up, 

 and are indeed hardly yet in full working order. 



