August 27, iqo8] 



jVA TURE 



405 



would be no particular difficulty in maintaining any tliesis 

 if results could be treated in this way. 



Mr. Fletcher's work has been partly on the above lines. 

 He obtained a " solution of excreta " by growing plants 

 in water culture, and then used this solution as a medium 

 for plant growth. It proved to be to.xic, and the con- 

 clusion is drawn that the plant first used excreted some 

 poisonous body. The experiment, however, is not a very 

 good one. It is well known by those who have worked 

 with water cultures that bacterial decompositions are liable 

 to take place in the solution, producing substances injurious 

 to plants ; precautions always have to be taken to prevent 

 development of bacteria, 'it does not appear that any 

 such precautions were taken by Mr. Fletcher, indeed, the 

 conditions under which he worked seem to have been 

 favourable to bacterial development ; well water was used, 

 and the " solution of e.xcreta " was allowed to evaporate 

 at ordinary temperature until sufficiently concentrated for 

 the second part of the experiment. There is no evidence 

 that the toxic substance was excreted by the plant ; it 

 might equally well have been a bacterial product. 



In another set of experiments crops were grown in rows 

 side bv side, and three lots of measurements were t.aken : — 

 (i) the yield in the outside row, bordering on the bare 

 ground ; (2) the yield in the middle row; (3) the yield in 

 a row bordering on another crop. The first is the highest, 

 the second shows the effect of the plant on others of the 

 same kind, and the third shows the effect on others of 

 a different kind. The falling off in yield in the second 

 and third cases is regarded by Mr. Fletcher as proof of 

 a toxic excretion ; it is generally explained as due to lack 

 of w-ater or food, and no satisfactory evidence is adduced 

 against this view ; indeed, Mr. Fletcher states that the 

 reductions in crop are less marked under a more evenly 

 distributed rainfall. We cannot consider that the question 

 of root excretion has been materially advanced in any of 

 these publications. E. J. R. 



ACID-RESISTING ALLOYS. 

 A P,'\PER was read at a recent meeting of the Faraday 

 ■'"^ Society by Mr. Ad. Jouve describing the remark- 

 able resistive character of ferro-silicon and other silicon 

 allovs. .Attention was directed to the fact well known 

 to analysts that no methods of analysis for this sub- 

 stance, based upon the use of acids, with the exception 

 of hydrofluoric acid, are employed for ferro-silicons, 

 because ferro-silicon containing more than 20 per cent. 

 of silicon is insoluble in acids. This protective property 

 of metalloid is being made use of in producing acid-resist- 

 ing vessels. Ferro-silicons, however, are not the only sub- 

 stances which possess this property ; almost any alloy of 

 a metal with this metalloid will behave in the same way 

 to a greater or lesser degree, according to the nature of 

 the metal. Calcium-silicide is, for example, unaffected by 

 acid, whereas calcium itself acts vigorously upon water. 



.As showing the resistance of these alloys, which are 

 called " Metillures," to acids, the following example is 

 interesting : — Xitric acid, even as a vapour such as is 

 obtained at the exit of a bisulphate retort or when mixed 

 with nitrous acid, does not affect them at all. A striking 

 example of this is given by a pipe which has been sub- 

 mitted for nearly five years to the daily passage of 660 lb. 

 of nitric acid vapour at temperatures varying from 150° 

 to 200° C. without its loss in weight exceeding a few 

 decigrams in a total weight of a score of kilograms. 

 This loss occurred quite at the beginning of the period, and 

 was probably due to a few impurities remaining on the 

 inner surface of the pipe after fusion. 



Sulphuric and hydrochloric acid appear to have still 

 less effect, and pines of ferro-silicon have been used for 

 carrying and condensing gaseous hydrochloric acid. Acetic 

 acid and the mixture produced by tre.ating calcium acetate 

 are also without action. Seeing the extremely high price 

 of platinum, which is the most stable of all industrial 

 metals, it would appear probable that the advent of these 

 new resisting alloys will become of very considerable 

 importance. The chief drawback to their use is in the 

 brittleness and weight of the alloy, the vessels made of 

 it being generally rather thick. 



NO. 2026, VOL. 78] 



CERTAIN ASPECTS OF THE WORK OF 

 LORD KELVIN.' 



WHEN" a man of the first magnitude works continually 

 at a single group of subjects from an age preceding 

 twenty to an age exceeding eighty, the circumstance is so- 

 exceptional and the output so enormous that no ordinary 

 summary or criticism can do it justice. _ 



I shall not aim at any chronological sequence, and, in 

 fact, propose to begin with those later physico-philosophic 

 views which seemed to determine the direction of his- 

 thoughts and the attitude of his mind to nascent and con- 

 temporary discoveries in recent years. 



For this aspect, even if difficult to treat of, is one which, 

 a biographer is bound in some fashion or another not to 

 shirk ; and, although myself unable to regard it with full 

 sympathy, I am confident that my point of view is neither 

 presumptuous nor disrespectful. 



Kinetic Theory of Solidity. 



Now, I confess that for some years before his death Lord' 

 Kelvin's attitude to fundamental physical or philosophical 

 questions was somewhat of a puzzle to me. He seemed 

 to be abandoning ground which he himself had opened 

 up to explorers, and discouraging others from advancing, 

 in directions where he himself had pioneered. As a matter 

 of fact, I was uncertain whether his position was even con- 

 sistent and logically tenable or not ; and at the British- 

 ,-\ssociation meeting at Leicester, during a discussion on 

 the constitution of the atom in Section A, I had an op- 

 portunity of respectfully and deferentially challenging him 

 on this subject. He responded, as always, in the kindest 

 manner, and with great and almost exceptional lucidity 

 indicated what had now become his position. I would not 

 be understood as implying that he carried conviction, or 

 led me to regard that position as a desirable one to 

 occupy ; but he showed it to be a consistent and logical 

 one, which he had every right to occupy if he chose, and 

 on which, therefore, it must be left for posterity, or at 

 least for effluxion of time and progress of discovery, to 

 pass anything in the nature of ultimate judgment. 



I was muclf interested in this pronouncement, andbefore 

 leaving Leicester jotted dow-n a few notes concerning it, 

 with the view of publishing them in his lifetime, in order 

 that he might, if he chose, add to, or subtract from, or 

 modify the statement. Other things prevented rapid pub- 

 lication, how-ever, and accordingly it is too late for one 

 of the objects in view, but still the notes are worth pub- 

 lication as suggesting genuine antithetical or alternative 

 views of the universe. (They have now appeared in 

 N.^TURE for July 2, 1908.) 



It may seem as if the real antithesis was between the 

 postulates of a connecting medium, on the one hand, and 

 of action at a distance across empty space, on the other, 

 and as if Lord Kelvin were in favour of the latter view. 

 I do not, however, think it would be fair to attach to 

 him that responsibility. I think it was more a matter 

 of practical politics, with him, than a philosophical con- 

 ception. I think he would have liked to see an explana- 

 tion in terms of a connecting medium, if it could have 

 been managed ; but, after spending some years in the at- 

 tempt, he abandoned it either as too difficult or as hope- 

 less, and constrained himself to be satisfied with unexplained 

 forces between masses of matter acting according to speci- 

 fied laws ; the question of the medium or mechanism 

 through which thev acted being left out of account as 

 unnecessary from the point of view of practical dynamical 

 calculation and consistent reasoning. 



He did speak at times, however, as if immediate action 

 across empty space would be logically satisfactory to him, 

 and quite good enough as an explanation ; the only ques- 

 tion being, was it the true one? To me I confess that 

 anv such philosophic scheme must necessarily be a cold 

 and merely descriptive account of material activity — that 

 it must necessarily fail to go to the heart of the matter 

 or to constitute what may more reasonably be called " ex- 

 planation." The conception of forces acting according to 

 a specified law of distance is capable of yielding dyna- 

 mical results truly, but not of explaining them. Ex- 



1 Abridged from the presidential address 10 the Faraday Society, 

 delivered by Sir Oliver Lodge, F.R.S., on May 26. 



