October io, 1890.] 



SCIENCE. 



203 



crease of 54 schools and 3,647 scholars during the ten years from 

 1879 to 1889. It would seem, therefore, that tlie decennial in- 

 crease of schools and scholars during the last twenty yeax-s has 

 shown a tendency to keep up with the jirogressive increase of 

 population. Comparing the statistics of individual years, the 

 number of schools under supervision and examination by the in- 

 spector of schools rose from 94 in 1837. and 97 in 1888, to 104 in 

 1889, while the number of scholars under instruction in these same 

 schools ro=e from 5,974 in 1887, and 6,258 in 1888, to 7,107 in 1889. 

 There is, therefore, a steady annual increase during the last three 

 years, progressing from an increase of 284 scholars in 1888 to an 

 increase of 849 in 1889. The expenses incurred by the government 

 ^ ■during theyear 1889, on account of education in general, amounted, 

 •exclusive of the cost of new school-buildings, to a total of $53,901. 

 — Mr. E. Nevill, the government chemist at Natal, in his last 

 jrepoit to the colonial secretary, notes that valuable deposits of 

 argentiferous galeno of copper and of bismuth exist in the colony, 

 and of such rich nature that they could be profitably exported in 

 ba]k. In both Alexandra and Umvoti Counties, as stated in 

 Nature of Sept. 25, deposits of silver-bearing lead ore have been 

 ifound containing from ten to fifteen pounds' worth of silver per 

 ton of lead ore. Saltpetre has been found so rich as to be worth 

 iffiore than three times as much as the best Peruvian deposits. 

 Plumbago, asbestos, and the mineral phosphates appear to be of 

 inferior quality. Several calcareous formations have been exam- 

 ined, which are likely, under proper treatment, to yield good hy- 

 draulic cement. 



— Some chemical re-actions can be started or accelerated by 

 '.sunlight, and an increased effect is to be expected where the rays 

 are concentrated by a lens or concave mirror. Herr Briihl has 

 described experiments made in this way, in production of zinc 

 ■ethyl from zinc and ethyl iodide, — a re action difficult to start. 

 As given in Nature, the retort, containing zinc filings and several 

 liundred grams of ethyl iodide, was placed at the focus of a con- 

 cave mirror, about a foot in diameter, receiving the sun's rays. 

 The re-action soon began, and grew so vigorous that cooling was 

 necessary. In a quarter of an hour all the ethyl iodide was con- 

 iconsumed, and, through the subsequent distillation in an oil-bath, 

 a good yield of zinc ethyl was had. This radiation process, it is 

 suggested, might be variously useful in actions on halogen-com- 

 3)0unds, which tend to be disaggregated by sunlight A lens, 

 .owing to the athermanous property of glass, wguld be less power- 

 ful. 



— Lord Eayleigh has recently had under observation, says 

 Engineering of Sept. 26, some eases of defective color- vision which 

 prove, what seems only natural, that we cannot simply distin- 

 ^'guish trichromJc and dichromic color-vision, as has .sometimes 

 Ibeen done. Normal color-vision is trichromic; color-blin.d people 

 liave dichromic vision. If we have black, white, blue, red, green, 

 we can match two against three. For dichromic vision we want only 

 four colors; for instance, those mentioned without white. For ordi 

 nary purposes the wool test will suffice: if not, we recur to spin- 

 niiig disks, — two concentric disks, the one over the other, the 

 inner one consisting of sectors of different colors, the outer one 

 showing ring portions. The disks are made of colored cardboard, 

 and have a radial slit, so that we can make up any combination 

 we like; e.g., 10 parts of black -f 45 white-f 35 green, 100 making 

 the total circumference. Sometimes patients prove obstinate, and 

 -will not say when they consider the inner and outer disk matches. 

 Such are examined by means of an older apparatus of Lord Ray- 

 jleigh's, a color-box with a revolving Nicol. Here they often 

 ■commit themselves, and discover differences of brightness only, 

 where t3iea:e are evident differences of color. As an example of a 

 peculiar match, Lord Eayleigh gave the following: 64 green -)-36 

 blue = 61 black -f-39 white, that is. a green-blue against a gray; 

 another, 82 red -f 18 blue (crimson) =32 green -|- 78 blue. But such 

 people are not always consistent in their way: they will n ake 

 certain matches, but refuse to acknowledge others which appear 

 .'Suited for them. One case, for instance, first thought to be di- 

 ■chromic, finally proved not to be so; the sensibility for red not 

 lieing altogether absent, but only impaired. Such cases have been 

 little studied as yet. Lord Eayleigh further referred at the meet- 



ing of the British Association, at which his paper was delivered, 

 to Maxwell's color-triangle, and the position of the black and the 

 dark spot. 



— The last two numbers of Cosmos contaiu some very interest- 

 ing information on various topics. Some new discoveries have 

 been made at Pompeii, near the Stabiana Gate, and a description 

 is given of them. Nature states that three bodies were found, 

 two being those of men, and the third that of a woman. Not far 

 from the resting-place of these bodies was found the trunk of a 

 tree, 3 metres in height, and measuring 40 centimetres in diameter. 

 This tree, together with its fruits that were found with it, have 

 been examined by the professor of botany, M. Pasquale, who finds 

 in it a variety of Lauriis nobilis. By means of the fruits, since 

 they come to maturity in the autumn, he concludes that the erup- 

 tion did not take place in August, but in November. 



— It vvas observed a short time ago by Dr. Kremser, says 

 Nature of Sept. 25, that the curve of mortality in North Germany 

 lagged about two months behind that of the variability of tem- 

 perature. An inquiry into this matter in the case of Budapesth 

 has been lately made by Dr. Hegyfoky, taking the nine years 

 1873-81. Comparing the months, he failed to make out a certain 

 connection; but taking into account other meteorological elements 

 besides temperature, and reckoning by seasons, he found the 

 variability of weather in the different seasons to give the follow- 

 ing order from maximum to minimum: winter, spring, autumn, 

 summer. As regards mortality, the order was spring, summer, 

 winter, autumn. Thus it appears there is a displacement of three 

 months. If a connection of the kind referred to really exists be- 

 tween weather and mortality, the effect (mortality) must appear 

 somevihat later than the cause (variation of weather). 



— We learn from Engineering of Sept. 26 that the Forth Bridge 

 has been for some time entirely completed, the works have been 

 dismantled, and the engineers' staff and the workmen have had 

 to seek new fields of operation, some of the engineers having gone 

 to Mexico, America, Greece, and India. The finishing touch, it 

 is interesting to note, is the only thing in the way of ornament on 

 the bridge, all else being indispensable parts of the structure. 

 This embellishment consists of two brass plates placed on the 

 south cantilever pier, in commemoration of the opening of the 

 bridge by the Prince of Wales on March 4, 1890. The names of 

 the du-ectors, engineers, and contractors are also given. Sir John 

 Fowler has had fitted at the end of the south main span, at which 

 point the contraction and expansion joint is placed, an indicator 

 to record the number of trains passing and the daily contraction 

 or expansion of the bridge. The apparatus consists of a brass 

 rod, with a pencil, attached to the end of the girder, and a clock 

 with another brass rod fixed in its axle. Round the rod in the 

 axle of the clock is wound a strip of paper about four inches wide, 

 with a weight attached to the end. The point of the pencil rests 

 on this paper, which is, of course, constantly on the move as the 

 clock winds down. The result is, that as the cantilever contracts, 

 the pencil attached to it is pulled away; when it expands, the 

 pencil is pushed forward; and a curve of contraction and expan- 

 sion is thus produced by the movement of paper and pencil com- 

 bined. The same principle is applied to register the behavior of 

 the bridge while a train is passing. When the train enters on the 

 one end of the cantilever, it pulls the far-off end down; and when 

 it does so, it also pulls the pencil, and thus a mark at right angles 

 to the curve of contraction and expansion is made. When it 

 passes t(5 the other half of the cantilever, it pushes it forward, 

 and again a mark at right angles to the curve is made on the 

 other side. Each mark indicates a train, and thus the simple 

 apparatus serves three purposes. The management are troubled 

 a good deal with requests for passes to inspect the bridge; but as 

 walking over the bridge, owing to the narrowness of the side- 

 walk, is attended with considerable danger, very few are granted. 

 The speed of the trains in crossing the bridge is not now limited, 

 except in the case of goods trains, and with them it must not ex- 

 ceed twenty-five miles an hour. As there are only about two feet 

 six inches between the pedestrian on the bridge and the flying 

 train, it is seen that the precaution is wise. The average traffic 

 on the bridge amounts to about one hundred and forty trains daily. 



