374 



NATURE 



[July ii, 191; 



fly, which annually destroys about 80 per cent, of the 

 crop. Small wooden boxes are fastened to the tree, 

 and beneath the cover of each box is fixed a bunch of 

 straw. The straw is spread with an insecticide, of 

 which the formula is given. The result has been to 

 reduce the losses to 10 per cent. 



For the: past few years Swedish seaweed has been 

 coveted by the Germans, who, by chemical treatment, 

 made it into fodder, and also extracted valuable 

 chemical products from it. A number of experiments 

 have been made at Stockholm, according to the 

 Svenska Dagbladet for May 12, and it has been found 

 that by dry distillation of i kg. of dried seaweed the 

 following substances can be extracted : — 30 to 32 litres 

 of illuminating gas, 43 per cent, of carbon, 45 per cent, 

 of distillates (acetic acid, methylated spirit, formic acid, 

 acetone, etc.), 14 per cent, of salt (sodium sulphate, 

 potassium sulphate, potassium chloride), also iodine, 

 bromine, a very arorhatic tar product, and carbolic 

 tar (creosote?), an excellent preservative of timber. A 

 factory is about to be started by the Focus Co. to take 

 up the conversion of seaweed on a large scale. 



When a sphere or other solid symmetrical about an 

 axis performs torsional oscillations about that axis in 

 a viscous liquid it is found that the logarithmic decre- 

 ment of the oscillation is not constant until the oscil- 

 lation has died down to less than 001 radian, and 

 becomes difficult to measure with the necessary 

 accuracy. Determinations of the viscosity of the 

 liquid from the v&lue of the decrement on the assump- 

 tion that the oscillations died away according to the 

 simple exponential law have generally given too high 

 results. In Communications from the Physical 

 Laboratory of the University of Leyden, No. 151, Dr. 

 VerschafTelt shows both theoretically and experi- 

 mentally that the oscillations require at least three 

 terms of the form e -««;«, where e is 2718, t is the time, 

 n has the values i, 3, 5, etc., and fe is a complex 

 quantity involving the viscosity of the liquid. VVith 

 this theory as a basis he is able to show that the 

 viscosity of liquid hydrogen at 20° Absolute is ooooii — 

 that is, about one-hundredth part of that of water at 



15° c. 



Up to ten years ago our knowledge of the distribu- 

 tion of the electric potential in a vacuum tube through 

 which a discharge was passing was derived from ob- 

 servations with an exploring electrode, but in 1909 

 Sir Joseph Thomson introduced the more trustworthy 

 method of determining the electric field in a tube by 

 discharging cathode rays across it and measuring the 

 deflection of the rays produced by the field. Using 

 this method, Aston in 19 10 found the field in the 

 cathode dark space proportional to the distance from 

 the edge of the negative glow, while Harris in 1915 

 found it increased much moro rapidlv as the 

 cathode was approached. Messrs. T. Takamine and 

 I'. Yoshida, in the October issue of the Science 

 Memoirs of Kyoto University, give the results of their 

 measurements of the field in narrow tubes by the 

 widening or separation of spectral lines photographed 

 across the field, a method due to Lo Surdo. Thev 

 find that the field at a point distant d from the end 

 of the dark space exceeds the field at the end by a 

 quantity proportional to d^. The curves given in the 

 paper show that this law is a close approximation to 

 the facts. 



The May issue of the Lyonian (the magazine of the 

 Lower School of John Lyon, Harrow) contains the 

 report of a lecture on " Chemical Change " delivered 

 by Mr. O. A. Le Beau at a meeting of the school 

 scientific society. The lecturer commenced by pointing 



NO. 2541, VOL. lOl] 



out that chemical change is of universal and never- 

 ending occurrence, and then differentiated it from 

 physical change. The five different types of chemical 

 change, direct union, decomposition, polymerisation, 

 single replacement and double replacement, were 

 defined, and so far as possible illustrated by experi- 

 ment. The phenomenon of catalytic action was shown 

 experimentally, and also the action of light upon 

 chemical change. Such a recent development of the 

 action of electricity as the production of "active 

 nitrogen " was illustrated by a repetition of Prof. 

 Strutt's original experiment. We think it com- 

 mendable that the school possesses a science master 

 who evidently keeps abreast of modern research, and 

 that such a lecture, involving much work in its pre- 

 paration, should be so enthusiastically received. 



We have received a reprint from the Journal of the 

 West of Scotland Iron and Steel Institute of a paper 

 recently read by Dr. Desch on "Attempted Improve-' 

 ments in the Puddling Process." As Dr. Desch points 

 out, the process of manufacturing malleable iron by 

 means of puddling, invented by Henry Cort in 1784,- 

 has undergone surprisingly little alteration in the 

 course of its history. It is still performed in units of 

 small size owing to the fact that manual labour is 

 employed fqr the manipulation of the metal, and the 

 quantity dealt with cannot exceed that which a man 

 can handle without the aid of machinery. Certain 

 details of Cort's original process have been modified, 

 and have produced an important effect on the develop- 

 ment and manufacture, but the principle has remained 

 unchanged. The present report does not deal with 

 such improvements as those which have led to the 

 puddling furnace of the present day, but is an attempt 

 to collect information concerning proposals which have 

 aimed at altering the character of the process, either 

 by lessening the manual labour involved or by in- 

 creasing the thermal efificiency of the furnace. Few 

 of these suggested improvements, however, have been 

 adopted permanently even on a limited scale, and the 

 type of furnace in universal use differs less from that 

 used at the beginning of the nineteenth century than 

 from most of the proposed substitutes for it. Un- 

 doubtedly the most important of these modifications 

 was the Danks furnace, which was a practical suc- 

 cess, and its failure to maintain its ground was due, 

 not to anv inherent defects, but chiefly to the abandon- 

 ment of iron-making in favour of steel by those firms 

 which had formerlv shown the greatest interest in the 

 problem, and had come nearest to solving it. Dr. 

 Desch 's paper is an interesting summary of the sub- 

 ject, and should be of great service. 



The assistance which America is rendering to thfe 

 Allies in the matter of shipbuilding is illustrated by 

 articles in the Engineer and Engineering for June 28, 

 descriptive of the world's largest shipyard at Hog 

 Island, on the Delaware. The land on which this 

 shipyard stands was virgin on September 20, 1917; 

 the twenty-first slipway is now in use, and twenty- 

 nine other slipwaj's are in course of construction. A 

 shipyard capable of havin.cf fifty ships on the stocks 

 at one time was a thing quite undreamt-of until last 

 year, and suggested the visions of Jules Verne rather 

 than the plans ot sane business men. Yet it is now 

 in a fair way of accomplishment, and the estimate 

 may be accepted of fiftv ships being built simul- 

 taneouslv, while twenty -eight others are being fitted 

 out at seven piers each of a length of 1000 ft. When 

 that stage is reached there will be a launch every other 

 day, either of a 7500-ton cargo ship or of an 8000-ton 

 combined troop and cargo boat. The site covers 

 84.6 acres, and extends over two miles of river front. 

 The various parts of the vessels are being " fabri- 



