August i, 1907] 



NA TURE 



335 



mutual inductance, and therefore attraction, of sucli 

 circuits, has appeared in the May Bulletin of the Bureau 

 of Standards at Washington. In one of these the various 

 expressions which have been given for the mutual induct- 

 ance of co-axial solenoids, from that due to Maxwell to 

 the one Mr. A. Russell gave in the April number of the 

 Philosophical Magazine, are compared and tested. Un- 

 fortunately, none of them appears to be at the same time 

 accurate and easy of numerical calculation, while in one 

 or two of them the authors have detected small errors. 



Publication No. 62 of the Carnegie Institution of 

 Washington consists of an account by Prof. Carl Barus 

 of the work he has done on the condensation of vapour 

 as induced by nuclei and ions. The condensation is 

 effected in a cylindrical glass fog chamber 6 inches in 

 diameter and 18 inches long, by exhaustion into a vacuum 

 chamber through a stop-cock 4 inches in diameter. The 

 coronas produced in transmitted light by the fog are 

 observed through a goniometer. Different gases have been 

 tried as well as different saturating vapours. In all cases 

 there appear to be three types of condensation nuclei, 

 dust particles, transient bodies which when charged are 

 the ions, and lastly, e.xcessively minute and persistent 

 " colloidal " nuclei, on which condensation only takes 

 place at the higher exhaustions. Prof. Barus has not 

 found any daily period in the number of colloidal nuclei 

 present in the atmosphere which could be ascribed to 

 cosmical radiation. In this respect they differ from the 

 ions, which have been shown by Messrs. A. Wood and 

 A. R. Campbell (Nature, vol. Ixxiii., p. 583) to be present 

 to the maximum extent about 9 a.m. and noon, and to 

 reach a minimum about 3 p.m. 



Dr. E. Grimsehl describes in the Physikalische Zeit- 

 schrift for July 15 a simple apparatus suitable for demon- 

 strating the principal properties of electric oscillations. 

 Condensers of various sizes are formed by placing two 

 sheets of tinfoil between three sheets of ebonite and 

 vulcanising the whole together, leaving metal ears project- 

 ing so that each condenser can be hung on two bare 

 wires which form part of the circuit. Variable inductances 

 are made of solenoids of hard copper wire, one end of 

 each being fixed and the other attached to a slide which 

 can move parallel to the axis of the solenoid, so as to 

 vary the length. The spark gap is formed by two 

 aluminium spheres at the ends of two brass screws which 

 pass through opposite sides of an ebonite box. With this 

 apparatus and, for waves in wires, a simple Hertz 

 generator capable of being tuned, almost all the funda- 

 mental experiments on electric oscillations can be per- 

 formed. 



The curious differences of colour exhibited by the thin 

 films of gold produced on the surface of a glass plate near 

 which a gold wire is slowly disintegrating owing to the 

 passage of an electric current through it, have been ex- 

 plained by M. L. HouUevigue in a communication to the 

 Soci('t(5 Franijaise de Physique at the last meeting (July 15). 

 Films which appear blue in transmitted light are composed 

 of a hydride of gold, stable at ordinary temperatures, but 

 unstable above 130° C, when it loses 7 per cent, to 8 per 

 cent, of its weight. Such a film when heated is con- 

 verted into the more commonly known form, which appears 

 to be identical with beaten gold leaf, and is green in 

 transmitted light. Several other properties of these films 

 find a simple explanation in M. Houllevigue's discovery. 



The Board of Agriculture has issued the ninth part of 

 the memoir descriptive of the South Wales coalfield 

 (Memoirs of the Geological Survey, price 8d.). The volume 



NO. 1970, VOL. 76] 



covers fifty pages, and is an explanation of the new series 

 map, sheet 246, which includes West Gower and the 

 country around Pembrcy. The report has been drawn up 

 by Dr. A. Strahan, F.R.S., in part from notes by Messrs. 

 B. S. N. Wilkinson, T. C. CantriU, and E. E. L. Dixon. 

 The dominant feature in the structure of the district is the 

 anticline which throws up the Old Red Sandstone to form 

 Cefn-y-Bryn. The Old Red Sandstone appears under an 

 aspect that was quite unexpected. The red marls that 

 form the lower half of the formation around most of the 

 coalfield are absent in parts of Gower, whilst the con- 

 glomerates at the top attain a remarkable development, 

 and Silurian rocks come to the surface as an inlier. The 

 Carboniferous Limestone is well developed. On the coast 

 between Llanelly and Pembrey, the lower part only of the 

 Pennant series is exposed, but the whole of the Lower 

 Coal series probably exists under the estuary of the 

 Loughor. The probable effect of various anticlines and 

 synclines upon the extent of the Coal-measures under that 

 estuary is taken into consideration and illustrated in a 

 map. The only coal seams hitherto worked are those 

 which are developed in the Pennant series in the western 

 part of the South Wales coalfield, and the value of the 

 concealed and unproved coalfield is lessened by the fact 

 that the strata are likely to be highly inclined and much 

 disturbed. The superficial deposits include the Raised 

 Beach, which is so finely exhibited in East Gower, and 

 glacial deposits, both presenting features of great interest. 



We have received the eleventh of a series of bulletins 

 published by the Engineering Experiment Station of the 

 University of Illinois. It deals with the effect of scale 

 on the transmission of heat through locomotive boiler 

 tubes, and has been drawn up by Prof. E. C. Schmidt and 

 Mr. J. M. Snodgrass. Of late years there has been much 

 discussion on the subject, and statements as to the extent 

 to which deposits of scale affect the conductivity of a tube 

 or sheet have been made from time to time, and have 

 differed widely. The results of the authors' tests lead 

 to the following conclusions : — Considering scale of 

 ordinary thickness, say of thicknesses varying up to 1 inch, 

 the loss in heat transmission due to scale may vary in 

 individual cases from insignificant amounts to as much 

 as 10 per cent, or 12 per cent. The loss increases some- 

 what with the thickness of the scale. The mechanical 

 structure of the scale is of importance equal to or greater 

 than the thickness in producing this loss. Chemical com- 

 position, except in so far as it affects the structure of the 

 scale, has no direct influence on its heat-transmitting 

 qualities. 



We have received from Mr. R. Lavachery, a Belgian 

 engineer residing at Chapultepec, Mexico, drawings of an 

 ingenious appliance invented by him for life-saving at sea. 

 It consists of a rifled cannon from which a projectile is 

 fired ; to the projectile are attached a cable, an anchor, 

 and a rocket. The mechanism is very simple, and for 

 humanitarian reasons the inventor has not patented it. 



Benjamin Robins, F.R.S., is remembered as the inventor 

 of the ballistic pendulum and as the founder of the 

 modern science of gunnery. As the details of his life and 

 work are not generally known, opportunity is taken by 

 Kngineeriiig (Julv 19), in the year of the 200th anniversary 

 of his birth, to give detailed particulars of his career. 

 Though he only lived to the age of forty-four, yet in that 

 time Robins was in turn mathematical tutor, civil engineer, 

 scientific experimenter, political pamphleteer, editor of 

 " Anson's Voyages," and, at last, engineer-in-chief to the 



