382 



NA TURE 



{Feb. 1 6, I 



of course the country intervening between this limit and the 

 coast always consists, more or less, of a slope. Roughly speak- 

 ing, it may be said that in the south and north there is a more 

 or less gradual slope from the height of land to the coast, while 

 in the south-east the descent is sudden, and almost immediately 

 after leaving the tableland there is reached a level which is but 

 little above that of the sea. In the north-east portion the edge 

 of the tableland approaches nearest to the coast, while it trends 

 considerably to the west in the rear of Hamilton Inlet. The 

 most fertile part of the country is that which lies between the 

 tableland and the sterile belt on the coast, though the height of 

 land itself is by no means a desert. On the height of land there 

 is found a succession of great lakes joined together by broad 

 placid stream^. When the streams of water reach the edge of 

 the tableland, they of course commence a wild career down 

 towards the sea. In- the case of the Grand River this rapid 

 ■descent commences with the Grand Falls, and almost the whole 

 of the great drop to the sea-level is effected in the one waterfall. 

 The elevation of the Labrador tableland is given by Prof. Hind 

 as 2240 feet. From this height the Moisie and Cold Water 

 Rivers descend to the sea by means of a considerable number of 

 falls. But in the Grand River below Lake Waminikapou there 

 is only one fall, viz. that which occurs 25 miles from the river- 

 mouth. This fall is 70 feet. It is true that the whole of the 

 river from Lake Waminikapou to the First Falls is rapid, but 

 there is no place wliere there is any considerable drop, and 

 indeed no place where it is necessary to take the boat out of the 

 water. Now the lake first above the Grand Falls is on the 

 height of land. In the channels joining the various lakes above 

 the falls there are no rapids and there is scarcely any stream. 

 It therefore follows, assuming the elevation of the tableland on 

 the east to be approximate to that on the south, that in the 30 

 miles beginning with the Grand Falls and ending with Lake 

 Waminikapou, there is a drop of about 2000 feet. Some of this 

 drop is probably effected by the rapids immediately below the 

 falls, but the greater part is no doubt made by the fall itself 

 The river is said by Maclean to be 500 yards broad above the 

 falls, contracting to 50 yards at the falls themselves. The 

 interior of the country Mr. Holme found was richly wooded, and 

 the climate mild, though the plague of flies and mosquitoes was 

 almost "intolerable. The few Indians who inhabit Labrador 

 belong mostly to the Cree nation, and according to Mr. Holme 

 are probably perfectly unmixed with either whites or Eskimo. 

 As an agricultural or pastoral country Mr. Holme thinks 

 Labrador has no future, though something may be made of its 

 iron, of the existence of which strong indications exist. Mr. 

 Holme's observations have enabled us greatly to improve our 

 maps of Labrador, and the photographs he brought home give 

 an excellent idea of the general character of the country. 



OUR ELECTRICAL COLUMN. 



Some very interesting and remarkable trials of the trans- 

 mission of energy were recently made between Kriegstetten and 

 Solothurn in Switzerland, by Prof. H. F. Weber and others, 

 when it was found that 30 horse-power put in at the first place 

 delivered 23 horse-power at the other, 8 kilometres away — 

 showing an efficiency of 75 per cent. The current, 11 amperes, 

 driven under an E. M. F. of 2000 volts, showed absolutely no 

 Joss whatever, owing to the use of Johnson and Phillips' " oil " 

 insulators. This mode of insulation proved absolutely perfect. 



The distribution of electricity for lighting purposes by means 

 of secondary generators, is now being discussed at the Society 

 of Electrical Engineers. This mode of working seems to have 

 solved the question of the economical erection of conductors. 

 Alternate currents of high tension in the main conductors allow 

 wires of small diameter to be used, and a special form of induc- 

 tion coil transforms these currents of high tension, 2000 volts, 

 to currents of low tension, 100 volts and under, for use in 

 private houses. The system, due to Messrs. Gaulard and Gibbs, 

 is in use at the Grosvenor Gallery installation, as well as at 

 Eastbourne and Brighton, and is probably going to be largely 

 used. Mr, Kapp's paper " On Alternate Current Transformers, 

 with Special Reference to the Best Proportion between Iron and 

 Copper," will lead to an interesting discassion. All induction 

 coils, when used as transformers, are simply a magnetic circuit 

 or closed iron core interlaced with an electric circuit or a closed 

 copper core, and constructed so that the electric circuit shall 

 embrace as many as possible of the lines of force of the mag- 



netic circuit. Mr. Kapp divides transformers into two classes 

 — one in which the copper coils are spread over the surface of 

 the iron core as in a Gramme armature, and the other in 

 which the iron core is spread over the surface of the copper 

 coil. The former he calls "core transformers," and the latter 

 "shell transformers." He advocates working transformers at 

 low inductions — that is, far below the point of saturation of iron 

 — because it increases the plant- efficiency, reduces the heat or 

 energy lost in the iron core through hysteresis, and prevents the 

 production of sound. The plant- efficiency of transformers 

 sometimes reaches as high as 99 per cent. , and they are perfectly 

 self-regulating. There is very little choice between core- and 

 shell-transformers, but the former have the advantage. Economy 

 in construction and facility in manufacture and repair seem to 

 be principal points of advantage to reach. It is amusing to find 

 how, now that the system has proved to be practical, every man 

 is devising his own transformer, and labouring to show that 

 Gaulard and Gibbs were not the inventors of the system, and 

 that their transformers are not the best. 



Prof. Ewing's discovery of hysteresis in iron has been 

 shown, both by Kapp and Ferrari, to play a very significant 

 figure in the efficiency of transformers. 



GUGLIELMO, of Turin, has shown that no loss of electricity 

 takes place through moist air surrounding an aerial wire unless 

 the E.M.F. exceeds 600 volts, after which the leakage increases 

 with the E.M.F. and the saturation of the air. 



In Boston an electric lamp has recently been used to search 

 for a body drowned in the harbour. The U.S. steamship 

 Albatross is furnished with a full complement of lamps for 

 fishing. The glow-lamp is encased in a wire netting, which 

 acts as a trap. The fish, being 'attracted by the light, swarm 

 into the net, which is then closed and pulled in. 



The new number just issued (No. 201) of the Proceedings of 

 the Royal Society contains the following electrical papers : 

 " On the Photometry of the Glow-lamp," by Captain Abney 

 and General Festing ; "On the Development of Feeble Cur- 

 rents," by Dr. Alder Wright and Mr. C. Thompson ; and " On 

 the Heating-Effects of Electric Currents," by Mr. Preece. 



MAKING GLASS SPECULA B V HAND} 



'T*HE author of this paper gives a very interesting account 

 of the construction of glass specula, discusses the actual 

 difference in form between a spherical and a parabolic mirror, and 

 gives an account of some experiments to determine the thickness 

 of the silver film. In making the specula Mr. Madsen used 

 glass for the grinding tool in place of metal, as he considered 

 'hat the coefficient of expansion of iron and glass being different, 

 greater truth would be obtained by the use of the same material 

 for the tool, thus following the practice of Foucault and of the 

 French opticians of the present day. When a true spherical 

 surface was thus obtained the polish was given by rouge on pitch 

 with a tool the same size as the mirror, and the correction of 

 the spherical curve was obtained by a very ingenious plan of 

 graduating the polisher in such a way that the greatest action 

 would be on the required part of the mirror, the arrangement 

 of the squares of pitch being such as to prevent the occurrence 

 of rings of unequal polish. In this Mr. Madsen seems to have 

 been most successful. 



In working, the mirror was uppermost, and this is a very 

 important point in many respects. There is no doubt that in 

 working this way the mirror is in the condition of least strain, 

 and if it were possible this plan should always be followed, but 

 it is absolutely impossible to do this with a mirror much larger 

 than the size he worked, which might almost be taken as the 

 limiting size of mirror possible with this method of working. 

 Short, Mudge, Herschel, and all the early workers used this 

 plan in making their comparatively small mirrors ; but since, 

 with larger sizes, the mirrors have been worked face upwards as 

 the only possible way, and it is to be regretted that this plan 

 was not followed. 



In discussing the actual amount of the glass to be abraded to 

 obtain the correction, the author finds that for telescopes where 

 the focal length exceeds twentytimes their diameter this amount is 



' " Notes on the Process of polishing and figuring 18-inch Glass Specula 

 by Hand, and Experiments with Flat Surfaces," by H. F. Madsen. 

 (Journal and Proceedings of the Royal Society of New South Wales, 

 vol. XX., 1886, pp. 79-91). 



