464 



SCIENCE 



|Vol. IV., No. 93. 



volume, notwithstanding so much space is given 

 to large illustrations. Many of the latter are 

 extremely amusing. One of them (p. 85) rep- 

 resents a street in New York lighted by the 

 Brush electric lamps. On the pavement are 

 many mercurial New-Yorkers, waving their 

 hats ; and one is so much overcome with en- 

 thusiasm, that he turns his back upon the fait 

 accompli, and walks away with bared head. 

 Should not this engraving be entitled ' A street 

 in Paris ' ? 



Report on the International exhibition of electricity, 

 held at Paris, August to November, 1881. By 

 David Porter Heap, major corps of engineers, 

 U.S.A. Washington, Government, 1884. 287 p. 



8°. 



It will be interesting to the visitor to the 

 Philadelphia electrical exposition to compare 

 his recollections of that exhibition with Major 

 Heap's report of the Paris exposition of 1881. 

 He will find in this latter work a short and con- 

 cise account of the principal types of dynamo- 

 machines, and will discover that the new forms 

 which were exhibited at Philadelphia differ only 

 slightly from those described b}- Major Heap. 



The report does not pretend to contain an}' 

 measurements or calculations, and was neces- 

 sarily somewhat hastily prepared. The elec- 

 trician, however, will find it a valuable addition 

 to his library. 



ABC de la pholograpMe mod erne. Par W. K. 

 Burton, C.E. Traduit de l'anglais par G. Hu- 

 berson. Paris, Gauthier-Villars, 1881. 112 p. 

 12°. 



As its name implies, this work is intended 

 for the beginner in photography, but it con- 

 tains many hints that those of longer experi- 

 ence might profit by. Beginning with the 

 choice of apparatus, and the arrangement of 

 the dark room, the whole process of photog- 

 raphy is described, including both methods of 

 development, to the production of the finished 

 print. The most prominent defect of the 

 work is that the chapters on printing are rather 

 too brief: indeed, there is no description at all 

 of the processes of mounting and burnishing. 

 The chapters on the production of the nega- 

 tive, however, are excellent, as is the one on 

 defects and their remedies. 



NOTES AND NEWS. 



Professor Mell, director of the Alabama weather- 

 service, announces, that through the liberality of the 



chief signal-officer, and of several railways, daily 

 weather-signals, predicting cbanges of weather and 

 temperature, will be displayed at over one hundred 

 telegraph-stations in that state. The predictions will 

 be received by the director at an early hour every 

 morning from the signal-office in Washington, and 

 then promptly distributed along the railways. By 

 paying for the cost of the signal-flags (about six dol- 

 lars), any town or telegraph-station will receive free 

 telegraphic warning of the daily weather-changes. 

 Only about five minutes is required to set the flags. 

 A similar system has been for some time in operation 

 in Ohio and in part of Pennsylvania, and it will 

 doubtless have farther extension. 



— Herr Warburg has succeeded in electrolyzing 

 glass by heating a piece of soda-lime glass to about 

 300° C, at which temperature it is a conductor, and 

 placing it between mercury electrodes. It was neces- 

 sary to use from fifteen to thirty Bunsen cells for a 

 long period. He then found, that, at the anode side of 

 the glass, he had a layer of silicic acid. This layer 

 very quickly reduces the strength of the current, 

 owing to its bad conductivity. 



— We learn from Nature that a tunnel measuring 

 about five thousand feet in length, and constructed 

 at least nine centuries before the Christian era, has 

 just been discovered by the governor of the Island 

 of Samos. Herodotus mentions this tunnel, which 

 served for providing the old seaport with drinking- 

 water. It is completely preserved, and contains 

 water-tubes of about twenty-five centimetres in diam- 

 eter, each one provided with a lateral aperture for 

 cleansing-purposes. The tunnel is not quite straight, 

 but bent in the middle : this is hardly to be wondered 

 at, as the ancient engineers did not possess measur- 

 ing-instruments of such precision as those constructed 

 nowadays. 



— Heddebault has succeeded in separating rags 

 of cotton and wool, mixed, by subjecting them to the 

 action of a jet of superheated steam. Under a press- 

 ure of five atmospheres, the wool melts, and sinks to 

 the bottom of the receptacle; while cotton, linen, and 

 other vegetable fibres stand, thus remaining suitable 

 for the paper-manufacture. The liquid mud which 

 contains the wool thus precipitated is then desic- 

 cated. The residue, which has received the name of 

 azotine, is completely soluble in water, and is valu- 

 able on account of its nitrogen. Moreover, its prepa- 

 ration costs nothing; because the increased value of 

 the pulp, free from wool, is sufficient to cover the cost 

 of the process. 



— A Berlin correspondent of the St. James gazette 

 writes that an engineer named Pisher is reported to 

 have made an important discovery in aeronautics, by 

 which he is enabled to condense or expand the gas in 

 a balloon. The agent he employs is compressed car- 

 bonic acid, with the help of which he can ascend or 

 descend at pleasure. This perpendicular movement 

 puts it in the power of the aeronaut to go up or down 

 until he finds a current of air moving in the horizon- 

 tal direction he wishes. Military critics attribute 

 great importance to this discovery, because in time of 



