September 13, 1889.] 



SCIENCE. 



179 



tricts could be eliminated from the calculation, the figure would, of 

 course, drop considerably. Still more remarkable would the sani- 

 tary condition appear if the area were confined to the high and 

 airy suburbs in which so large a proportion are fortunate enough 

 to dwell. Londoners have only to contrast this condition of things 

 with the statistics of other capitals, to see how great is the advan- 

 tage they enjoy. In Paris, which shows a comparatively good 

 record, the mean annual death-rate is 32.1 ; in Berlin it is 27.5; 

 in Vienna, 26.7 ; in Munich, 32.9, and in St. Petersburg, 43.7. In 

 Brussels, which appears to be the healthiest of continental cities, it 

 is 18.9. To sum up the case, the death-rate during the quarter in 

 twenty-nine colonial and foreign cities, having an aggregate popu- 

 lation exceeding 16,000,000 persons, was 26.6 per 1,000, or more 

 than loi persons per 1,000 in excess of the London death-rate. 



— The Iowa Academy of Science held its third annual meeting 

 at West Des Moines on Sept. 5. Among the papers presented 

 were the following : " Life History of Le/andrz'a ignoia" by Mr. 

 F. W. Malley; "The Blue Quail in Iowa," "The Mission of Sci- 

 ence," and " Notes on the Geology of North-western Iowa," by 

 Professor J. E. Todd ; " Fossils of the Keokuk Beds," by Professor 

 C. H. Gordon ; " Pearl Rearing Unios " and " Rearing Vanessa 

 antiopa," by Professor F. M. Witter; "Native Forest Trees of 

 Eastern' Arkansaw " and " Geology of Eastern Arkansaw," by R. 

 Ellsworth Call ; " Geology of North-eastern Iowa," by Dr. P. J. 

 Farnsworth ; " Notes on Beggiatoa," by Professor L. H. Parmmei ; 

 " Distribution of Hemiptera," by Professor Herbert Osborn ; " Is 

 the Plum CurcuUo double-brooded .' " by Professor C. P. Gillette ; 

 "The Food-fishes of Iowa," by Professor Seth E. Meek ; and " The 

 Crystalline Rocks of Missouri," by Professor Erasmus Haworth. 

 Professor Todd also exhibited some volcanic dust from a stratum 

 near Omaha. 



— Schemes for irrigation in Upper Egypt have been considered 

 by Colonel Ross, inspector-general of irrigation, with the governors 

 of the provinces and the provincial councils. According to E7igi- 

 neering, the area affected by these proposals includes 736,000 

 acres, of which no less than 250,000 acres were not irrigated or 

 were insufficiently irrigated in iSSS. The projects are all based on 

 the idea of going up the river to such a distance that a canal start- 

 ing at that point shall, when the Nile is at fourteen cubits, take 

 enough water and deliver on the surface a free flow. The present 

 system of canals is being utilized by deepening, widening, and pro- 

 longing them, and in many cases only by a change of site of the 

 offtake from the river. The masonry works required will, it is esti- 

 mated, cost about §900,000, of which $500,000 is required immedi- 

 ately. The junctions and prolongations of canals are estimated to 

 cost about a million dollars. The length of the valley to be thus 

 protected from the effects of a low Nile is 255 miles. 



— Mr. William Crookes, in the course of a presidential address 

 to the Chemical Society, said : " The phosphoroscope affords an- 

 other method of verifying the simple or compound character of a 

 substance. It is well known that the continuance of phosphores- 

 ■pence after the cessation of the exciting cause varies widely, from 

 some hours, as in the case of the phosphorescent sulphides, to the 

 fraction of a second in the case of uranium glass and quinine sul- 

 phate. On examining phosphorescent earths glowing in a vacuum 

 tube under the action of the induction discharge, I found remark- 

 able differences in the duration of this residual glow. Some of the 

 earths, after the cessation of the current, remain luminous for an 

 hour or more, whilst others cease to phosphoresce immediately on 

 the stoppage of the current. Take the case of yttrium. As al- 

 ready stated, I succeeded in resolving this earth into several sim- 

 pler bodies not equal in basicity. While seeking for further proof 

 of the distinct character of these bodies, I observed that the after- 

 glow differed somewhat in color from that which the earth exhib- 

 ited whilst the current was still passing. Further, the spectrum of 

 the after-glow seemed to show, so far as I could judge by the faint 

 light, that some of the lines were missing. As this phenomenon 

 indicated another difference among the components of yttrium, I 

 examined them in an instrument similar to Becquerel's phosphoro- 

 scope, but acting electrically instead of by means of direct light. 

 Under ordinary circumstances it is scarcely possible to perceive 

 any phosphorescence in an earth until the vacuum is so high that 



the line spectrum of the residual gas begins to grow faint. Up to 

 this point, the stronger light of the glowing gas overpowers the fee- 

 ble glow of the phosphorescence. But in the phosphoroscope the 

 light of the glowing gas lasts only for an inappreciable time, while 

 that of the phosphorescent earth persists long enough to be dis- 

 tinctly observed. The different bands of the new constituents of 

 yttria do not all appear at the same speed of rotation. At the low- 

 est speed the double greenish blue band of G/3 is first seen, fol- 

 lowed next by the dark blue band of Ga. As the velocity in- 

 creases, there follows the bright citron-yellow band of Grf, and as 

 the utmost speed approaches the red band of Gf is seen, but with 

 difficulty. If lanthanum sulphate along with a little lime is exam- 

 ined in the phosphoroscope, the line of Ge is visible at the lowest 

 speed; G(5 follows at an interval of 0.0035 second, and the Ga line 

 immediately afterwards." 



— Professor Frank D.Adams, having been appointed lecturer 

 on geology in McGill University, Montreal, is about to sever his 

 connection with the Geological Survey of Canada. 



— A most interesting exhibit at the Paris Exposition, according 

 to Engi7ieering, is a recording flash telegraph for military or other 

 purposes. This apparatus, which is exhibited by MM. Ducretet, 

 is in fact a combination of a flashing telegraph and a Morse printer, 

 consisting of a projector fitted with a powerful lamp in the focus 

 of the usual optical apparatus. In front of the lamp and below it 

 and the lenses is a screen, which may be suddenly removed from 

 the front of the lamp by the depression of a key similar to that in 

 use under the Morse system, and this screen may be as suddenly 

 replaced by the release of the key ; the flashes, long or short, are 

 therefore transmitted to the distant station by the action of the key 

 exactly in the same way as in transmitting a Morse message. The 

 movement of the key has, moreover, a second action, for it sets 

 into motion or stops the Morse recorder, doing mechanically ex- 

 actly what the electric current does in the ordinary form of that in- 

 strument. As long as the key is depressed a beam of light is con- 

 tinuously projected to the distant station, and a continuous line is 

 drawn on the paper band, and the moment that the key is released 

 the light is obscured, and at the same time the recorder ceases to 

 draw a line on the paper. Thus every flash, whether short or long, 

 as well as the periods of rest, are accurately recorded on the band 

 of paper, and a permanent record is produced of every message 

 flashed through the instrument. 



— The " chemin de fer glissant," or sliding railway, at the Paris 

 Exposition, says the Engineering and Mining Journal, is the ap- 

 plication in practice of an old theory that, by adopting a sled upon 

 rails with water interposed as the.carrying medium, the least pos- 

 sible friction would be encountered and greater speed could be at- 

 tained than by means of wheels. The promoters of the enterprise 

 give the credit of the invention to a French engineer named Girard, 

 who was killed in the Franco- German war, and name as the date 

 of it 1868 ; but, if we are not mistaken, the idea was advanced 

 some years before this date in England, where it was looked upon 

 as chimerical and impracticable. However that may be, it has 

 now for the first time been tried on a working scale, and in combi- 

 nation with a system of propulsion which, we believe, is novel. 

 The wheels are replaced by four hollow slides, about eight by four 

 inches, one at each corner of the car, fitting upon a flat and wide 

 rail, grooved on the inner surface. To set the car in motion, water 

 is forced by compressed air into the slide, which it raises slightly 

 from the rail, and the propelling force is supplied by a stream of 

 water at high pressure directed from short iron pillars upon pad- 

 dles fixed underneath the car. The stream of water is supplied 

 automatically by the movement of the car, being shut off in the 

 same manner by the paddle passing out of range. By the time 

 the last car has passed the jet the foremost one has reached the 

 next pillar. The force developed is represented as verj' great. 

 The train is stopped by shutting off the stream of water that feeds 

 the slides. The experimental line on the Esplanade des Invalides 

 has four carriages, with seating capacity for about a hundred 

 passengers, and to traverse its length, some two hundred and fifty 

 yards, only a few seconds are required. Great speed is claimed for 

 the invention, not less than about ninety miles an hour, and the 

 ability to stop in thirty yards when running at this speed. Gradi- 



