November 14, [91! 



NATURE 



215 



ssary to preveni friction between kelp-harvesters 

 .iikI fishermen desiring to use the beds ai the same 



time. 



Attention ma) be directed to .1 papei on the 

 inn of the potato plain, with special reference 

 to the ontogenj of the vascular system, bj E. F. 

 Artschwager, published in vol. xiv., No. 0, of the 

 journal of Agrii ultural Research. The study was 

 undertaken primarily to serve as a basis for work on 

 that obscure disease 01 group <>( diseases, possibl) 

 to which the name "leaf-roll" has been given; and 

 there can be no doubl thai a serious scientific inves- 

 tigation ol the nature ami causes of this trouble is 

 one of pressing importance for all countries where the 

 potato is grown. The paper referred to will be found 

 useful as a convenient summan of previous 

 work cm the anatomy of tin potato plant, and in somi 

 directions it throws new light on points which were 

 formerl) not altogether clear. The importance of the 

 development of secondary phloem is emphasised, anil 



shown thai the increase in size of the tuber is due 

 nion 1.1 the formation of new tissue in the peri- 

 medullary zone than to growth of the pith, as was 

 formerly supposed. It is clearh shown that the skin 

 of the tuber is composed of periderm derived to some 

 extent from the original epidermis, as well as from 

 tlie hypoderm. The paper is illustrated by twenty-one 

 1 photomicrographs, as well as by a 



■ st-figures. 



In the Journal of the Washington Academj of 



11 r 4 Messrs. P. 1). Foote and. T. R. 



Harrison, of the Bureau of Standards, in a paper on 



some peculiar thermo-electric effects, point out that 



the production of a thermo-electric current in a 



tetricallj was 



known to Franklin and Cavendish a hundred and 



tift\ years ago. It continues to be "rediscovered' 



tde, but up to the present time not one of 



the mam causes which have been suggested for the 



has pro\ed satisfactory. The authors state, 



however, th form 1 if tie' experiment 



in which a hot and a cold piece of the same metal 



are brought ion of the current 



nected with the sign of the Kelvin 



Mi;. I.. B. AtKINSO Kelvin lecture to the 



Institution of Electrical Engineers on November 7. 

 lb- chose as bis subject The Dynamical Theorv of 

 Electric Engini S," and began by quoting a formula 

 for inductance or "electromagnetic capacity" which 

 Kelvin gave in the i860 edition of Nichol's "Cyclo- 

 paedia" (see Thomson's "Reprint," p. 44 ;)■ He sug- 

 I that this formula and the equally well known 

 in for the mutual action between electric 

 circuits when their currents an maintained con- 

 looked by electricians, who 

 mereh considered what mat be called the statical 

 theorv of the dynamo. Mr. Atkinson then de- 

 betw een the cj cle of an elei ti 1 1- 

 ngine and the cycle of a reciprocating 

 engine, deducing what appeared to us to be verj 

 curious formula- for the efficiency of the various cycles. 

 He excused his neglect of the resistance of the wind- 

 ings of the electrii b\ pointing out that in 

 uture some material of vei : sistanci ma 



I from which they can bi made. Nothing 



said either about hysteresis or armature reaction. 



In order that Kelvin's theorem might apply, Mr. 



Atkins suppose that tie- currents in the coils 



Were , 5 • t,ip|e integt a! 



formulae well known to mathematicians were given for 

 tie energj stored up in the field, but wi 

 - 559, vol. 102] 



follow what usi le made of them. It is difficult to 

 see how the method developed can be .if am practical 

 use. It maj be pointed out that the dynamical theorv 

 of the dynamo has been developed le Lyle, Russell, 

 and several French electricians, who have based solu- 

 tions on the conservation of energj and inductance 

 formulae on the lines laid down by Kelvin. Their 

 results take cognisance of both resistance and arma- 

 ture reaction, and are in close agreement with experi- 

 ment. As in all other theories, however, the assump- 

 tion is made that the iron has consta ibility. 



Among the books mentioned in the new announce- 

 ment list id Messrs. Longmans anil Co. we notio 

 fallowing:— Eoihr Chsmictrj J II- 1 ml uh 

 nil-. "The Natural Organic Colouring Matters," 

 Prof. A. G. Perkin and Dr. A. E. Everest; "Catal 

 in Industrial Chemistry," Prof. G. <;. Henderson; 

 "Plantation Rubber," (.. S. Whitby (Monographs on 

 Industrial Chemistry). "The Rare Earth Metals," 

 Dr. J. F. Spencer, and a new edition of "Osmotic 

 Pressure," Dr. A. Findlay (Monographs on Inorganic 

 and Physical Chemistry). "Naval Architects' Data," 

 J. Mitchell and E. L. Attwood; "Experimental Educa- 

 tion," being a new and enlarged edition of "Introduc- 

 tion to Experimental Education," Dr. R. R. Rusk; 

 and "Economic Reconstruction," J. Taylor Peddie. 



The following additions will shortly be made to the 

 series of "Military Medical Manuals," edited 1- sir A. 

 Keogh (Hodder and Stoughton) : — " Commotions and 

 Emotions of War," Prof. A. Leri, edited by Sir John 

 Collie; "Disabilities of the Locomotor Apparatus, the 

 Result of War Wounds," Prof. A. Broca, transl 

 b\ Capt. J. R. White ami edited by Sir Robert Jones; 

 " Electro-diagnosis of the War," Prof. A. Zimmern 

 and P. Perol, translated by L. P. Garrod and edited 

 by E. P. Cumberbatch; "Mental Disorders of the 

 War," Prof. J. Lepine, edited by Dr. C. A. Mercier; 

 "Wounds of the Pleura and Lungs," Prof. R. Gregoire 

 and Dr. A. I dited le, Lt.-Col. C. II. Fa 



OUR ASTRONOMICAL COLUMN. 



Borrelly's Comet. — This comet is now quite an 

 object in a moderate telescope. Mr. R. L. Water- 

 field observed it at Cheltenham with a 4-in. refractor 

 early in November. It was brighter than 9th magni- 

 tude with central condensation, but no stellar nucleus, 

 diameter about 2'. The brightness will continue to 

 increase throughout November, and the increasing 

 north declination will facilitate observation. 



Orbits ok Two Spectroscopic Binaries. — Further 

 interesting investigations of spectroscopic binaries are 

 recorded in Bulletins Nos. 314 and 315 of the Lick Ob- 

 servatory. In the case of ^Velorum, magnitude 41, 

 < lass I- j, tin spi 1 tra of both components are exhibited, 

 and Dr. R. F. Sanford finds that the mass ratio is i-:;, 

 Adopting Russell's average mass for F stars of three 

 times that of the sun, the inclination of the orbit 

 would be 27 . With this inclination the semi-major 

 axes of the two orbits would be 10,880,000 km. and 

 [3,340,000 km. respectively. The period is 10-210955 

 days, and the eccentricity 0-541. From some of the 

 best spectrograms Messrs. Adams and Joy find the 

 absolute visual magnitude to be + 1-9 and the parallax 

 • 



The stai a Scorpii, magnitude 3-1, cla~s Hi, has 

 been it ed by Dr. F. I bin oteau, • 



confirms previous conclusions 

 m -In irtness id" the pei led. The si mi- 

 amplitude of each velocity curve bis tin- constant value 

 of 41-2 km. per second, but the velocity of the centre 

 of mass is variable, as if a third body wire present. 



