"Electrification of an Insulated Lens and Allied Problems treated by the Stream Function." By Sir GEORGE GREENHILL, F.R.S.

"Simultaneous Values of Magnetic Declination at Different British Stations." By C. CHREE, F.R.S.

A comparison is made of corresponding diurnal variations of magnetic declination at Eskdalemuir and Kew Observatories.

Mean monthly, daily, and hourly values of declination at Eskdalemuir, Stonyhurst, Falmouth, and Kew are compared. The results are also given of the measurements of a large number of irregular declination changes at the several stations.

It is found that the differences between different stations increase with the amount of magnetic disturbance, and that if accurate information is desired as to magnetic declination anywhere in the field, observations taken on disturbed days should not be relied on. It is thus important that observatory records should be consulted before the results of field observations are accepted.

A number of results are obtained as to the rela tive amplitudes of irregular declination changes at the several observatories.

"Symmetrisable Functions and their Expansion in Terms of Biorthogonal Functions." By J MERCER, M.A., D.Sc.

"Reduction of Error by Linear Compounding." By W. F. SHEPPARD.

The paper deals with the general problem of improving an observed quantity, which contains an unknown error, by adding to it a linear compound (linear function) of other observed quantities, called auxiliaries, the coefficients in the added portion being chosen so as to make the mean square of error of the whole a minimum. This is a generalisation of the special problem of finding the improved value when the auxiliaries are the differences, of sufficiently high order, of a set of quantities.

The treatment of the problem is simplified by brief statement of general theorems, and by a theory of conjugate sets of quantities. The fundamental theorem for reduction of error, from which others are easily derived, is that the mean product of errors of the improved value and each auxiliary is o. If , 1, 2 is a set of quantities containing errors, the conjugate set consists of quantities yo, 1, 2, . equal in number to the u's and connected with them by linear relations and such that the mean product of errors of ur and y's is if rs, and o if r and s are different. If the successive differences of the u's (commencing with a u) are regarded as a set, the conjugate set consists of sums, of successive orders, of the y's. The improved value of any linear compound of members of a set, using those after the first k as auxiliaries, is a linear compound of the first k of the conjugate set.

The object is to arrive at formulæ suitable for numerical calculation.

"Plane Stress and Plane Strain in Bipolar Coordinates." By G. B. JEFFERY.

The solution is given for a flat elastic plate, bounded by two circles, when under stresses applied over its boundaries. Curvilinear coordinates are employed for which the coordinate

curves form a double set of orthogonal coaxial circles. Important particular cases are: (1) a circular plate with an eccentric circular hole; (2) a semi-infinite plate bounded by a straight edge with a circular hole; (3) an infinite plate containing two circular holes.

The differential equation of the stress function is solved for these coordinates, and the stress function is obtained for given arbitrary stresses applied over the boundaries, and expressions are deduced for the stresses, and displacements produced at any point of the plate.

In illustration of the general method, the following problems have been specially considered : (1) a pipe with eccentric bore under given internal and external fluid pressures; (2) a plate with an unstressed straight edge and a circular hole under a uniform normal pressure; (3) a plate with a straight edge under a tension parallel to that edge, with an unstressed circular hole. The first two problems are solved in finite terms and the third in series, from which numerical tables are computed.

"The Tidal Motion in the Irish Sea, its Currents and its Energy." By R. O. STREET.

Certain general relations are obtained from the Laplacian dynamical theory connecting the form of the tidal wave and the magnitude of the surface current on a sea of limited extent rotating with the earth. In continuation of a former paper, these are applied to the recorded data for the Irish Sea, and the agreement is found to be fairly satisfactory. A second approximation to the hydrodynamical problem for a rotating tidal basin is then effected, and by means of the relations thus obtained, the mean rates of transfer of water and of energy across certain vertical sections placed transverse to the direction of the flood stream in the Irish Sea are computed from the existing hydrographical data. The results show that there is a residual flow of water northwards through this region of such magnitude that the Irish Sea would empty itself through the North Channel about three times a year, while the tidal flow of energy from all causes which takes place into this area is at the mean rate of about 6×10" ergs per second. The result of this estimate of flow of energy into the area is in general agreement with an independent one made recently by Mr. G. I. Taylor, Phil. Trans., A, 1919, ccxx., pp. 1-33. If we could assume that this energy is all dissipated, the result would be about 250 times the viscous dissipation calculated directly by the writer in a previous paper (Roy. Soc. Proc., A., 1917, xciii., pp. 348-359), on the assumption of smooth laminar tidal motion throughout the region.

"The Catalytic Activity of Copper." By W. G. PALMER.

Simple apparatus is described for the measurements by chronograph records of the reaction velocities at different temperatures of a typical catalytic action—that of the dehydrogenation of alcohol by copper. Details are given of the methods used in preparing a reproducible contact material. After oxidation and reduction a second time, the copper showed an activity of unchanged value.

It is shown that copper prepared electrolytically is quite inactive as a catalyst, in spite of great variation in the conditions of its deposition.

Copper reduced from its oxide was active at temperatures above 200° C., but this activity depended on the temperature at which the metal was reduced from its oxide.

Two curves have been constructed, showing the relation between temperature and catalytic reaction velocity for: (a) copper formed by reduction at the lowest possible temperature; (b) copper formed by reduction at 205° C.

The curve (a) shows a sharp change of direction at about 260° C., but the curve (b) is nearly a straight line, there being only a slight convexity towards the velocity axis. The form of these curves and the mechanism of the reaction are tentatively discussed and suggestions made for a continuation of the work.

"The Origin of the 'Cyanogen' Bands." S. BARRATT.

By

(i) Observations have been made of the spectra of the flames of a number of gases containing carbon, hydrogen, nitrogen, and oxygen.

(ii) The cyanogen bands are strongly developed in the coal-gas-nitrous oxide flame.

(iii) Evidence has been obtained that they are entirely absent from the hydrogen-nitrous oxide flame, if all traces of carbon are excluded, and it appears to follow that the presence of carbon is essential to their production.

(iv) The appearance of the cyanogen bands is, under appropriate conditions, a more delicate test for carbon than that of any of the other bands associated with that element. On the other hand, this spectrum is not necessarily developed when both carbon and nitrogen are present.

(v) The conclusion of Grotian and Runge that the cyanogen spectrum is to be attributed to nitrogen is shown to rest on assumptions which are not confirmed in the present investigation.

(vi) The cyanogen spectrum provides a very delicate test for the presence of compounds of nitrogen when admitted in the form of a gas to hydro-carbon flames burning in air, since elementary nitrogen does not appear, under ordinary circumstances, to be effective in producing the cyanogen bands in such flames.

(vii) The intensity of the cyanogen bands when carbon compounds are admitted to the hydrogennitrous oxide flame bears no simple relation to the amount of carbon thus added.

"Effects of Electron Collisions with Atmospheric Neon." By F. HORTON, Sc.D., and ANN C. DAVIES.

The critical velocities for electrons in neon were investigated by methods similar to those employed with helium and argon. It was found that neon differed from these gases in showing more than one critical velocity, both for radiation and for ionisation, these critical velocities being detected under conditions such as to preclude the possibility of any of them being due to the displacement or removal of a second electron from the atom. The critical values observed were:

A minimum radiation velocity of 118 volts. A minimum ionisation velocity of 167 volts. A second radiation velocity of 17.8 volts. A second ionisation velocity of 200 volts. A third ionisation velocity of 22.8 volts In obtaining these values special experiments were made to determine the correction to be added to the potential differences accelerating the elec

tron stream, so as to give the velocity of the electrons actually producing the effect observed at a critical point.

The experiments led to the conclusion that the radiation velocity of 11.8 volts is associated with the ionisation velocity 167 volts, and that the radiation velocity 17.8 volts is associated with the ionisation velocity 22.8 volts. These four critical velocities would be accounted for by the presence of two different kinds of atoms in the gas, either two different elements or two isotopes with different arrangements of the electrons surrounding the nucleus. The additional ionisation at 20'0 volts, which was not so strongly marked as the other effects, may perhaps be associated with a radiation velocity almost identical with one of those mentioned, or it may be due to a secondary effect arising from atoms having a radiation velocity of 200 volts. This latter possibility is discussed in the paper.

"Occurrence of Diatoms on the Skin of Whales." By A. G. BENNETT. With an Appendix by E. W. Nelson, M.A.

Mr. Bennett states that the skin of certain fin whales and blue whales captured in Sub-Antarctic waters is discoloured by a superficial film of a buff colour, resembling in tint the coloured bands often observed on floating ice. Whales thus affected are nearly always fat. Microscopic examination showed that this film consists of immense numbers of diatoms.

The fat individuals are probably those which have spent some time in the far south, where the supply of whale food is very abundant during the summer. There is reason to believe that the thin individuals are recent arrivals from warmer water. The skin of these thin specimens appears to be free from any noticeable film of diatoms; their light parts are thus white, instead of having the yellow tinge which has given rise to the name "Sulphur-bottom," applied by the whalers to whales in which the light parts are yellowish.

The cutaneous film of Antarctic Sulphurbottoms may be composed of the same diatoms as those which form the coloured bands on ice.

If

it can be proved that the outer surface of whales may become colonised by diatoms occurring in the waters frequented by them, the extended investigration of their skin may throw important light on their migrations by the study of the geographical distribution of the species of these microscopic organisms found on them. The demonstration of the nature of the deposit is further of interest in showing that whales differently coloured do not necessarily belong to distinct species. This may have a definite bearing on the question of the identity or otherwise of the species found in different localities.

Mr. Nelson's detailed examination of the specimens collected completely confirms Mr. Bennett's original observation as to the nature of the film. With the exception of one sample (which may possibly have been contaminated by diatoms from another source) all the films represented consist of diatoms of a single species, belonging to the genus Cocconeis, the members of which are usually found attached to submerged objects. The Cocconeis in question is described as a new species, and it thus gives no information with regard to the locality in which the diatom-infection originated.

"An Extension of the Balmer Series of Hydrogen and Spectroscopic Phenomena of very Long Vacuum Tubes." By R. W. WoOD, For. Mem. R.S.

"Moving Striations in Neon and Helium." By F. W. ASTON, M.A., D.Sc., and T. KIKUCHI.

When an induction coil spark is passed through a spectrum tube containing neon, and the discharge observed with a rotating mirror, it is seen to consist of bright striations moving from the anode towards the cathode. When first observed

the velocity was found to be roughly that of sound in the gas.

Further investigations now show that this is only a limiting case of a very complex phenomenon. The velocity is found to decrease with increase of pressure, and also to depend on the bore of the tube. The effect of change of temperature has been investigated, and curves are given showing that at constant volume the effect is much greater than the expansion coefficient. At constant pressure the temperature effect only comes in at high temperatures when it is probably due to impurities liberated from the tube.

Helium is found to give much the same sort of results as neon. Experiments with mercury vapour and other gases are also described.

No

satisfactory theoretical conclusions have yet been arrived at and further experiments are in progress.

NOTICES OF BOOKS.

Techno-Chemical Receipt Book. Compiled and Edited by WM. T. BRANNT and WM. H. WAHL, Ph.D. Pp. xxxiii+516. London: Hodder & Stoughton, Warwick Square, E.C.4. 1920. Price 15s. ret.

THE editor's aim in bringing this book before the public is to give an accurate and compendious collection of approved receipts and processes of practical application in the industries, and for general purposes. They have purposely excluded all theoretical reasoning and historical detail from the book, thus making it essentially a receipt book.

The book has been arranged alphabetically, but a copious table of contents as well as a good index are included so as to render the reference to any subject or special receipt prompt and easy.

Previous editions have been thoroughly revised, and this receipt book has been brought quite upto-date.

Bygone Beliefs. By H. STANLEY REDGROVE, B.Sc., F.C.S. Pp. xvi+205. London: Wm. Rider & Son, Ltd., 8, Paternoster Row, E.C.4. 1920. Price 10s. 6d. net.

THOSE interested in the early days of Alchemy should read Mr. Redgrove's book on "Bygone Beliefs". He takes the reader back to the mediæval times, and gives him representations of the superstitions and thoughts that were characteristic of the age.

The book is divided into twelve chapters each dealing with a belief or superstition of olden times, the explanations of which are helped by the interspersion of many illustrations.

CHEMICAL NOTICES FROM FOREIGN SOURCES.

Comptes Rendus Hebdomadaires de l'Académie des Sciences. Vol. clxx., No. 25. PRECIPITATION OF MERCURIC SALTS BY HYDROGEN SULPHIDE.-MM. Pierre Jolibois and Pierre Bouvier. When a solution of a mercuric salt is acted upon by sulphuretted hydrogen, a gradation in the colour of the precipitate can be noticed. These precipitates pass through a series of colourations from white to black. Polek and Gorki (Ber., 1888, xxi, 2412), have given the following formula for their composition:

2HgS,HgCl2; 3HgS,HgCl,; 4HgS,HgCl ̧. The authors have studied the composition of these coloured precipitates by using a solution of mercuric chloride of varying known strength precipitated by a 1/20th normal solution of sulphuretted hydrogen. The precipitate thus obtained was filtered off, dried, and the content of sulphur obtained by first oxidation with aqua regia and then precipitation as barium sulphate. The following table gives the result of their investigations:

THE Secretary of the Department of Scientific and Industrial Research begs to announce that the Research Association for the Silk Industry has been approved by the Department as complying with the conditions laid down in the Government scheme for the encouragement of industrial_research. As the Association is to be registered as a non-profit sharing company, the promoters have applied to the Board of Trade for the issue of a license under Section 20 of the Companies (Consolidation) Act of 1908. The Secretary of the Committee engaged in the establishment of this Association is Mr. A. B. Ball, The Silk Association of Great Britain and Ireland, Kingsway House, Kingsway, W.C.

THE CHEMICAL SOCIETY.-The lecture room at Burlington House, W., having proved to be entirely inadequate to accommodate the large audiences which attend the lectures, that on "Helium", by Professor J. R. McLellan, on June 17, was held in the lecture theatre of the Institution of Mechanical Engineers, by the courtesy of its Council. Sir J. J. Dobbie presided over an audience of nearly 250 and announced that the Emil Fischer Memorial Lecture would be given by Dr. M. O. Forster on October 21 next. He also made an appeal to British chemists to send donations (by July 31 at latest) in support of the memorial being raised by their French colleague to the memory of C. F. Gerhardt (1816-1856), the well-known French chemist. The subject matter of the lecture included data concerning the occurrence and content of helium in natural gas within the Empire, more particularly in Canada; the designs of the modifications of the Claude plant and process utilised, together with yields and possible applications. Prof. McLellan's latest experiments show that it is practicable to isolate on a commercial scale helium of 97 per cent purity from the natural gas at Hamilton, Ontario, at a cost of less than 24d, per cubic foot at Hamilton. A fuller account of the lecture will be given in these columns in due course. Sir Richard Threlfall, who spoke on the vote of thanks to the lecturer, stated that his suggestion to use helium in airships was communicated to the Admiralty as early as October, 1914, and that he was led thereto by press notices to the effect that the Germans were contemplating the use of an uninflammable gas. A search into the literature, especially into the investigations of Prof. C. Moureu on the dissolved gases in the springs of France, enabled him to show that the use of helium by the Germans was improbable, and then to present in outline a definite scheme of large-scale production from natural gas at Fredonia, Kansas, U.S.A., where the gas was known to be comparatively rich in helium. After a very full investigation, the Admiralty decided, in August, 1915, not to proceed with the scheme, but when America came in, all the information which had accumulated was passed on to that country.

THE BOHEMIAN GLASS INDUSTRY.-The glass factories are now overwhelmed with orders, partly

on account of the conditions of exchange and partly owing to the large business which resulted from the fairs of Leipzig and Lyons. In trade circles, however, the opinion is held that after two years of such activity over-production is bound to follow. Japan is to be regarded as a dangerous competitor; in 1914 that country had 463 glass factories and about 9000 workers, in 1917 there were 832 factories and 17,000 workers. In consequence of this competition, the Indian and most of the markets in the Near East are probably lost for good. New works have been erected in Belgium, the Ukraine, Rumania and Poland, and in north-west Bohemia alone 19 large new companies have recently been founded. All these facts point to a quick reaction for the local glass industry.-(Z. angew. Chem., April 20, 1920.).

ANNOUNCEMENT.-The Lord President, as President of the Council for Scientific and Industrial Research, has appointed Dr. J. S. Flett, F.R.S., at present Assistant to the Director in Scotland, to be Director of the Geological Survey and Museum. Dr. Flett succeeds Sir Aubrey Strahan, K.B.E., F.R.S., who retires this month, when Mr. G. W. Lamplugh, F.R.S., Assistant to the Director in England, also retires.

use

MILK PRODUCTS IN AMERICA AND EUROPE.-A recent investigation of this field is given in a report by W. Dempster, published in the New Zealand Journal of Agriculture, 1920, XX., 97-109. Milk powder is manufactured by the of heated rolls, or by spraying the previously concentrated milk into a hot chamber. In addition to its other uses in the food industries, skim milk powder or dried skim milk is used with butter in reconstituting milk and cream during seasons of scarcity of fresh milk. In the manufacture of reconstituted cream, the proper amounts of skim milk powder and water are placed in a jacketed vat and are intimately mixed by a propeller which revolves at a high speed. The speed is reduced, the proper amount of butter added, and the temperature of the mixture gradually raised to 145° F., kept constant for twenty to thirty minutes, then lowered to 135° F. The mixture is next put through a homogeniser, and immediately cooled to 45° F. In reconstituting milk, the skim milk powder and water are mixed as just described; the butter, which has been heated to a temperature of 120 F., is now forced through a spray nozzle which lies beneath the surface of the liquid; the finely divided butter fat is uniformly distributed throughout the reconstituted milk. Whole milk powder apparently does not keep well; it seems to require cold storage, e.g., o to -8° F., for its preservation. During the war, the production of lactose or sugar of milk increased enormously, since large amounts of that compound were used in the manufacture of smoke-shells. The casein industry of America centres in Philadelphia; this milk protein may be used as the basis of paints, which may be produced in any desired colour, withstand water, and retain their colour. The shortage of butter in England increased the demand for sweetened condensed milk, which was eaten spread on bread.-Journal of the Franklin Institute, June, 1920.