January 26, 1899] 



NA TURE 



301 



arranged in large, enclosed polyhedrons, the temperature to 

 which the rail was raised before rolling was too high. The 

 strength and intensibility increase as the size of the grain 

 diminishes ; and closely interlocking ferrite and pearlite repre- 

 sent the condition which most favours the prolongation of the 

 life of the rail. 



In connection with the works now being carried out for the 

 construction of the new Vauxhall Bridge, the contractors have 

 trected a suspension cable way across the Thames, for the 

 purpose of conveying material from the shore to the different 

 parts of the works. The length between the supports, each of 

 which is So feet above the ground, is 910 feet ; and the main 

 cable, which is made of steel, is 6t inches in circumference. The 

 cost of this cable way is about 2000/. 



A CIRCULAR, appealing for additional telegonic work, has 

 been sent to biologists, and others whose interest in the subject 

 is known, by Messrs. Alex. Meek and G. P. Bulman. In the 

 course of the note it is remarked : " After a careful study of the 

 facts already ascertained regarding telegony — that peculiar 

 phenomenon of cross-breeding, popularly termed " throw-back" 

 — we see that these can be attributed to reversion with almost as 

 much likelihood as to telegony." It is, however, believed that 

 telegonic effects are sometimes shown by the offspring ; but 

 more experiments are needed, and the circular indicates the 

 kind of information required.- Messrs. Meek and Bulman are 

 conductmg as many expermients as they can ; but telegony is 

 without doubt of extreme rarity, and the more trials that are 

 made, the greater is the chance of success. Those who will 

 assist are invited to send the skins of the parents and young 

 which display telegony ; also, in the case of birds, to send an egg 

 out of each batch. All communications should be addressed to 

 Mr. G. P.- Bulman, Durham College of Science, Newcastle- 

 upon-Tyne. 



Messrs. Mayer and MCli.kr, of Berlin, are publishing in 

 three volumes the mathematical correspondence of Gottfried 

 Wilhelm Leibnitr, under the editorship of C. J, Gerhardt. 



A CORRESPONDENT, Writing in the foiirnal of Applied 

 Microscopy, suggests that a convenient " pointer " for class 

 demonstrations with the microscope may be made by cementing 

 a human hair to the diaphragm of the eye-piece, projecting into 

 the centre of the field. A better plan would be to cement the 

 hair to a circular ring of blackened paper or cardboard, which 

 could be placed on the diaphragm or removed at will. 



A NEW bi-monthly journal has been started in Paris, bearing 

 the title V Rnseigue77tent Matiihnatique, It is to be devoted to 

 discussion of methods of teaching mathematics, with the object 

 of forming a medium of intercommunication between professors 

 and others engaged in this particular branch of teaching. The 

 first number bears the date January 15, 1899. The editors are 

 Dr. C. A. Laisant (Paris) and Prof. H. Fehr (Geneva), and the 

 publishers are MM. Georges Carre and C. Naud, 3 Rue 

 Racine, Paris. 



In the Nuoz'o Cimeiito, 4, viii,, Drs. V. Boccara and A. 

 Gandolfi describe experiments on the velocity of propagation of 

 Hertzian waves, undertaken for thepurposeof verifying the well- 

 known relation v = ij ^1 {kix). The media operated on consisted 

 of mixtures, in various proportions, of paraffin and finely pul- 

 verised iron. Both the magnetic permeability and the specific 

 inductive capacity could be increased by increasing the propor- 

 tion of iron, and the index of refraction for electromagnetic 

 waves was found to increase correspondingly, its value (h) being 

 given approximately by the relation « = i/ ^f {ifi). This relation 

 may, therefore, be regarded as verified experimentally. 

 NO. 1526, VOL. 59] 



A NEW departure in connection with projection microscopes 

 has been constructed for Prof. M. C. White, of Vale Univer- 

 sity, in the form of an objective of 20 mm. focal length, 

 and an estimated numerical aperture of o'gj. According to 

 ihe /oitniai 0/ Applied Microscopy, the new objective is a mag- 

 nified copy of a 5 mm. apochromatic, the diameters and radii of 

 curvature of all the lenses being increased fourfold. Dr. White's 

 theory is that if, in using the ordinary microscope, a certain 

 angular aperture is required to secure proper definition with a 

 magnifying power of, say, 1000 diameters, then a similar aper- 

 ture will be necessary to secure good definition in an image 

 projected on the screen, even if it is obtained with a three- 

 fourths-inch objective, and a projection eyepiece. The new 

 lens has been manufactured by the Bausch and Lomb Optical 

 Company. 



In experiments upon the discharge of negative electricity by 

 light, the electric arc is usually employed as the source of ultra- 

 violet rays, and a question arises as to how far such experiments 

 are affected by the electrical state of the vapours of the arc. The 

 Physical Review, vol. vii. pp. 129-148, 1898, contains an 

 arlicle on this subject by Messrs. Merritt and Stewart. It was 

 pointed out by Hallwachs, in 1890, that the protection offered by 

 a quartz window and wire gauze is in some cases insufficient to 

 screen the direct electrical action of the arc vapours from the 

 actino-electric apparatus. The electrical properties of the arc 

 vapours are similar to those of gases that have been acted upon 

 by X-rays, or to gases from a flame. It is supposed in these 

 cases that a condition is developed in the gas somewhat similar 

 to that in an electrolyte, i.e. ions are formed, some carrying 

 positive charges and others negative charges. This condition is 

 only temporary ; in the case of X-rays the gas loses this ionised 

 state in about one-tenth of a second. A charged body placed in 

 the ionised gas would attract one set of ions and repel the other. 

 Upon coming into contact with the charged body the ions are 

 supposed to give up their charges and to cease to exist as ions. 

 The experiments of Messrs. Merritt and .Stewart show that, 

 except at low potentials, the rate of discharge is not proportional 

 to the potential, but approaches a limiting value as the potential 

 is raised. The discharging power is retained even after the arc 

 vapours have been passed through long tubes of glass or of 

 metal, and lasts for at least ten seconds. There is some 

 evidence that the negative ions diffuse more rapidly than the 

 positive ones. If air or oxygen saturated with water-vapour is 

 introduced into the enclosure containing the arc, the conducting 

 power of the arc vapours is greatly increased. But this effect 

 can no longer be observed when the body to be discharged is at 

 considerable distance from the arc. 



From the Geological Survey uf Canada we have received 

 several essays reprinted from the Annual Report, vol. ix., 1898. 

 A report on the geology of the French River Sheet, Ontario, 

 by Dr. Robert Bell, is a concise explanation of one of the 

 Geological Survey maps (Sheet 125), printed in clear type, 

 accompanied by a colour-printed map on the scale of an inch to 

 four miles, and issued at the price of ten cents I Laurentian, 

 Huronian, Ordovician, and Silurian rocks are described, as well 

 as Glacial and other superficial deposits. Among " economic 

 minerals " it is observed that certain white quartzites would 

 furnish excellent material for making glass. 



Mr. a. p. Low reports on a traverse of the northern part of 

 the Labrador peninsula from Richmond Gulf to Ungava Bay. 

 Proceeding along the eastern shores of Hudson Bay, Mr. Low 

 explored Richmond Gulf, which is separated from Hudson Bay 

 by a high narrow ridge of Cambrian rucks, capped with trap, 

 and forming cliffs which rise 500 to 1200 feet above the water. 

 Between the Gulf and Clearwater Lake there is a plateau, having 



