458 



SCIENCE. 



[Vol. VII., No. 172 



America would be crowded as badly as the uni- 

 versal lamentations of medical men indicate, if 

 all were excluded from practice, save those who 

 had spent seven years in preparation. The course 

 of instruction at the Japanese college is modelled 

 after that of the German schools, and the lectures 

 are mostly delivered in the German language, by 

 the five foreign professors, though there is a spe- 

 cial course in the Japanese. The total number of 

 students in attendance last year was nine hundred 

 and seventy-two. 



— Messrs. W. T. Jackman and J. D. AVebster 

 have lately succeeded in obtaining good photo- 

 graphs of the retina of the living human eye, 

 illustrations of which are given in the English 

 Photographic news. They were able to bring the 

 time of exposure for the negative to within two 

 minutes and a half, and it is very probable that 

 technical skill will further reduce the time and 

 difficulties. The chief obstacles to shortening the 

 time of exposure, so far encountered, are the color 

 of the retinal reflection, and the fact that the lens 

 of the eye has the property of absorbing the ultra- 

 violet rays. It seems highly probable that the 

 photograph will here become a valuable adjunct 

 to the physiologist, ophthalmologist, or even the 

 general physician, as the eye affords diagnostic 

 aid in not a few diseases. 



— C. Wiegelt, O. Sacre, and L. Schwab have 

 made a series of very valuable experiments, says 

 the Chemical news, on the injury to fisheries and 

 fish-culture by sewage and industrial waste waters. 

 They find that chloride of lime, in proportions of 

 0.04 to 0.005 per cent chlorine, has an immediate 

 deadly action upon tench, while trout and salmon 

 perish in presence of 0.0008 per cent of chlorine. 

 Sulphurous acid has the same action as chlorine, 

 and is still more hurtful if another acid is simul- 

 taneously present ; sulphites are harmless. Hydro- 

 chloric acid, 1 per cent, kills tench and trout. In 

 sulphuric acid of 0.1 per cent, trout turn on their 

 sides in two to six hours, while tench were not 

 affected in eighteen hours. Acids are said to 

 have less action, the higher are their molecular 

 weights. Tannin at 0.1 per cent is 1 harmless. 

 Ammonia exerts no action at 0.01 per cent. Soda 

 at 1 per cent is fatal to trout on prolonged ex- 

 posure. Manganese chloride at 5 per cent had no 

 action on tench in twenty-two hours, and a trout 

 sustained 1 per cent for five hours. Iron acts as 

 a specific poison upon fishes, except in the state of 

 a feiTous salt. Alum has the same injurious ac- 

 tion as the salts of iron. Solution of caustic lime 

 has an exceedingly violent action upon fishes, due 

 in part to the deposition of calcium carbonate in 

 the gills. Arsenious acid, 0.1 per cent, combined 



with soda, has no injurious action upon trout and 

 tench. Mercuric chloride, in proportions of 0.1 

 and 0.05 per cent, is immediately fatal. Copper 

 sulphate, 0.1 and 1.0 per cent, kills trout in a few 

 minutes if they cannot escape into pure water. 

 Potassium cyanide, 0.01 and 0.005 per cent, is 

 rapidly, fatal if there is no escape. Potassium 

 sulphocyanide and ferrocyanide, in the proportion 

 Of 1 per cent, had no injurious action in an hour. 

 Sodium sulphide, 0.1 per cent, was endured by 

 tench for thirty minutes. The fish were bleached, 

 and did not recover their color in pure water. 

 Hydrogen sulphide proved rapidly fatal in the 

 proportions of 0.01 and 0.001 per cent. The hurt- 

 fulness of putrid sewage depends on poisonous 

 gases, on the deficiency of oxygen, and on the 

 action of bacteria. 



— The death is announced of Mr. Thomas Ed- 

 wards, the Scotch shoemaker naturalist whom 

 Dr. Smiles made famous. 



— In an article on coal-consumption as affected 

 by temperature and length of trains, the Railroad 

 gazette reaches some interesting conclusions. Dead 

 weight to the amount of thirty tons added to a 

 train of, say, five cars, will not increase coal-con- 

 sumption as much as to add another car, both 

 because it does not increase air-resistance and be- 

 cause the added load decreases somewhat the roll- 

 ing resistance per ton. If we assume it to add 

 five pounds per mile to the coal-consumption, we 

 are certainly not underestimating it proportionally. 

 Adding six tons per car, therefore, to the average 

 weight of a train of five passenger-cars, means no 

 more than an increase from fifty-five to sixty 

 pounds per train-mile. If we assume this five 

 pounds of coal to be worth one cent (at the rate 

 of four dollars per ton of two thousand pounds for 

 coal), and if an extra passenger at three cents per 

 mile be attracted to the train every third trip, he 

 will pay for the loss of fuel due to adding six tons 

 to the weight of every passenger-car, which goes 

 a little way toward explaining the tendency to 

 increase weight for the sake of luxury, which 

 seems so reckless. In this estimate, the effect of 

 extra weight on grade- resistance is taken into ac- 

 count, though in reality it is comparatively unim- 

 portant. It is estimated that about six pounds 

 and a half of coal per mile are added to the con- 

 sumption for each passenger-car of twenty tons or 

 more moved at way-train speed, and for each 

 sleeping-car of thirty tons or more moved in 

 through trains making few stops, and that the 

 locomotive alone is to be charged with rather 

 more coal than that due to three cars. 



— The discovery of an interesting illusory effect 

 in the sense of sight is given by Professor Exner 



