December 21, 1905] 



NA TURE 



181 



to have been the base of an ancient hearth in which the 

 metal had been subjected to repeated and prolonged heat- 

 in^-- 111.- metal contains, in addition to iron, 1-212 per 

 cent, of combined carbon, 003S per cent, of graphite, 

 1-670 per cent, of silicon, 0-026 per cent, of sulphur, 

 0013 per cent, of phosphorus, and o-iSo per cent, of 

 manganese. It is thus a steel containing a higher per- 

 centage of silicon than is now usual. The microscopic 

 examination shows that it belongs to Guillet's first group 

 ol silicon steels, pearlite steels consisting of a solid solution 

 1 I '.- S in iron. In the same issue Mr. A. Porlier gives 

 details of the composition of a cast-iron cannon ball found 

 in making the underground railway through the old moat 

 of the Bastille. The cannon ball was absolutely compact, 

 but oxidised throughout, its specific gravity being 4854 

 insfead of 7-6 as is usual for cast-iron. Under the micro- 

 scope the cementite appeared in brilliant lines, showing 

 that it had completely preserved its metallic state. The 

 oxidised portions, appearing as black masses, were derived 

 from the pearlite, which in admixture with cementite 

 constitutes ordinary white pig-iron. Analysis yielded: — 

 water, 2-9 per cent. ; carbon, 50. per cent. ; silicon, 0-25 

 per cent. ; manganese, 075 per cent. ; iron, 72-0 per rent. ; 

 and oxygen, 1745 per cent. The complete oxidation of the 

 cannon ball, without any exterior deformation or figura- 

 tion, shows the intense action of diffusion during a century, 

 and enables us to understand how the changes of rocks 

 by metamorphism have been able, thanks to the interven- 

 tion of infinitely longer periods, to give rise to new rocks 

 of a homogeneous structure. 



In No. 50 of the Bulletin 1U1 Musie ocianographique de 

 Monaco Prof. H. Hergesell gives an interesting account of 

 the method employed by the Prince of Monaco in the 

 North Atlantic last April for ascertaining the conditions 

 of the upper air by means of unmanned balloons sent up 

 from his yacht. Two closed india-rubber balloons were 

 employed ; at a certain altitude the upper balloon bursts, or 

 is set free by a simple electrical arrangement, when the 

 lower one, which carries the recording instruments, falls, 

 but has a float attached to it, at about 50 metres below 

 it, and when this reaches the surface of the ocean the 

 balloon is carried along by the wind at a height of 50 

 metres, and then the yacht has to chase it at full speed. 

 Out of five cases specified by Dr. Hergesell, only one 

 of the balloons eluded the pursuers. Of course, such 

 a procedure can only be undertaken by a vessel having no 

 other object in view, and it is necessary that the air should 

 be clear, and that the velocity of the wind should not 

 exceed the speed of the ship. Such experiments are 

 exciting, but expensive ; but some useful results at high 

 altitudes were obtained. 



A remarkable dam is under construction at Niagara 

 Falls, where the commissioners of Victoria Park, on the 

 Canadian side of the river, have erected a column of 

 concrete 50 feet high and 7 feet 4 inches square. This 

 column of concrete was built on a trestle that stands 

 20 feet above the ground-level, and after the material is 

 thoroughly dry the column is to be tipped over into the 

 river to form a dam. The necessity for this work arose 

 from the fact that the City of Niagara Falls, Ontario, and 

 the Niagara Falls Park and River Railway, made com- 

 plaint to the park commissioners that the works of con- 

 struction for power development had lowered the water 

 in the joint intake. The approximate weight of the con- 

 crete column is 200 tons. Every S feet of its height a 

 wooden wedge is inserted in the side, and passes nearly 

 NO. l886, VOL. 73] 



in Mi- centre, each wedge being about 12 inches thick on 

 tlie outside, tapering to about 6 inches near the centre. 

 The object of these wedges i- to break the column into 

 -ix pieces when it i> tipped over. However, these sections 

 will not lie allowed to be caught by the current, for 

 running up through the centre of the column thi 

 very heavy chain, the weight of which is about 800 lb. 

 The purpose of this chain is to hold the sections together 

 when the column is broken in falling. When it is pros- 

 trate, the top of the column will be 20 inches above the 

 ground-level, and is expected to raise the water in the 

 intake considerably. The intake is only about 600 feet 

 up from the brink of the Horseshoe Fall, but the dam 



will not affect the flow of the waterfall at that point. 



When dry, the column will be tipped by operating jacks 



under the base of the trestle, and when it tumbles it is 



expected to fall a little up-stream. 



We have received from Messrs. R. and J. Beck, Ltd., a 

 copy of their new illustrated price-list of telescopes. The 

 li-t contains particulars of numerous astronomical and 

 naval telescopes, object glasses, spectroscopes, transit 

 instruments, small observatories, diffraction gratings, &c, 

 and will be found to be very useful and suggestive to any 

 amateur astronomer who wishes to add a good instrument 

 to his equipment; some of the portable mountings, both 

 equatorial and altazimuth, appear to be very compact and 

 useful. A copy of a photograph of the iron spectrum, taken 

 with a " Thorp " transmission grating, shows the suitability 

 of these replicas for high-class work, and Messrs. Beck 

 undertake to mount the grating copies either on parallel 

 plate glass or on prisms of any desired angle. All kinds 

 uf surveyors' instruments are also quoted in this list. 



