742 



NA rURE 



[November 17, 1923 



?'ear» respectively, after which they will be returned 

 or examination and weighing. 



Meanwhile, lalxsratorv work on the same subject 

 18 l)einK tontintifvl, anrf the present report includes 

 a short but > ' communication from Dr. 



Friend on the i of strain on the corrodibility 



of iron and steel, \\lnch is of more than merely 

 technical interest. It has long Iwcn known that 

 iron, after lieing subjected to strain, is particularly 

 liable to corrosion, but little exact investigation has 

 been done on the subject. Dr. Friend has carried 

 out a series of expenments on sections cut from 

 bars that had been (>roken in the tensile tests carried 

 out for the committee. These bars represented 

 seven kinds of wrought-iron and steel, the chemical 

 and physical properties of which had been exactly 

 determined, as well as the degree of strain as measured 

 by the amount of elongation at the points at which 

 the sections were cut. The specimens, isolated on 

 parafhn blocks to prevent any galvanic action, were 

 exposed for a whole year to alternate wetting and 

 drying by tap water in a siphon tank, and the amount 

 of corrosion determined by weighing. The result 

 was, briefly, to show no difference in corrosion 

 between strained and unstrained sections except 

 in the case of a nickel steel (36 per cent. Ni) and less 

 clearly in a chromium steel (13 per cent. Cr). Both 

 these steels, and especially the latter, were very 

 resistant to corrosion, but the percentage difference 

 between strained and unstrained portions is described 

 as " extraordinarily great, resembling in magnitude 

 that observed when strained metals are subjected 

 to acid attack." Dr. Friend is careful to point out 

 that the uniform rates of corrosion in the other irons 

 and steels are not to be taken as contradicting 

 practical experience. In the tests electrolytic action 

 was carefully excluded, but in practice strained and 

 unstrained portions of the metal would be in con- 

 tinuous contact and the difference of potential so 

 produced might well account for the localised and 

 severe corrosion often observed. 



A very different field of work is that concerned 

 with the destruction of timber by animal pests, of 

 which the most important are the various kinds of 

 " shipworms " commonly referred to as Teredo. 

 Prof. George Barger reports on experiments in treat- 

 ing wood with various preservatives. The test 

 pieces, after impregnation with the poisonous solu- 

 tions, were " baited " by attaching a veneer of un- 

 treated wood, and were exposed to attack by Teredo 

 at Lowestoft. The most remarkable results were 

 obtained with an arsenic compound, phenarsazine, 

 known in poison-gas warfare under the names " D.M." 



and " Adarnsite." In i per cent, alcoholic ^ 

 thi^ compound entirely prevented the Tered 

 1 ig the test-blocks, although they wcr. 



I. in th«» veneer; even in a dilution of or 



per teat, the 1 n was all but complete 



Mr. C. R. 1 1 carried out at the Lab 



of the Mariii' al Association at Plymoinii 



some very u experiments on the larval 



development 01 i.i..i»j. The free-^- ■ •-- ' 



were kept alive for a fortnight, but ai 

 suitable food for them failed, and, ...1....,,.,^.. t,,, , 

 were attracted to and settled on shavings of wood, 

 it was not possible to observe th'-ir 1.. .nng. An 

 important and novel result was the of the 



manner in which they are attract* wood. 



It was found that alcohol and ether extract froin 

 wood a substance which has a strong chemotrnt.;. 

 action on the larvae. Photographs and diagr. 

 given to show how the larvse congregate r'. 

 small particle of the extract when it is placed ui the 

 dish in which they are swimming. Expmments were 

 then made with solutions of various pure substances 

 in capillary glass tubes closed at one end and placed 

 in sea water containing the larvae. Of the substances 

 tested in this way, malic acid was the only one 

 showing a very pronounced attraction. Whether 

 this is actually the attractive substance occurring 

 in wood, however, has not yet been ascertained. 



It is to be noted that neither Prof. Barger nor 

 Mr. Harington mentions by name the species of 

 Teredo used in their experiments, and the possi- 

 bility that the Lowestoft Teredo may be different 

 from that found at Plymouth is not even referred 

 to. Yet the zoological no less than the physical 

 or chemical data of the experiments deserve to be 

 determined with all possible precision. Closely allied 

 species of animals often differ widely in their physio- 

 logical reactions. One man's meat is another man's 

 poison, and, although no species of Teredo is likely 

 to grow fat on phenarsazine, it cannot be assumed 

 without trial that a poison efficient at Lowestoft 

 would be equally so at Colombo or even at Ply- 

 mouth. 



A contribution of a very different type is a " Rejxjrt 

 on Boring Organisms in various Waters " by Mr. 

 J. E. Cunningham of Sydney. It contains a series 

 of statements of the most amazing kind regarding 

 the natural history of Teredo. As an example we 

 may quote the assertion " that full-grown worms 

 will leave a piece of timber and enter another." 

 It is a great pity that the committee should have 

 thought fit to include a report of this character in 

 an official publication. 



Invention and Research in Mechanical Engineering. 



TV/TANY workers in applied science have an m- 

 •'•'-'■ terest in patents and patent law, and to such 

 the remarks made by Sir John Dewrance in his 

 presidential address to the Institution of Mechanical 

 Engineers on October 19 will be of value. Patents 

 and research have occupied a good deal of the pre- 

 sident's working life, and consequently they were 

 dealt with very comprehensively in his address. 



Some of the large engineering concerns of to-day 

 were started to work patented inventions, but if we 

 look back it is difficult to find very many of these 

 inventions that became the standard productions of 

 the industry when the monopoly expired. It has 

 become increasingly difficult to invent anything that 

 has not been foreshadowed in some previous publica- 

 tion. Patents have gradually become of less im- 

 portance in mechanical engineering. 



Sir John Dewrance has taken out 114 patents; 



NO. 2820, VOL. I 12] 



wnen a definite object is desired, the practice of his 

 firm has been to search its own records to see what 

 has been done before ; the Patent Office records are 

 then consulted. Various methods are then evolved 

 and discussed ; some of these get no further, whilst 

 others are made, tried, altered, and impro\ed, and 

 the result is exactly what has been felt ought to have 

 been done without all the trouble taken. If the 

 article finds a ready sale, an infringer may adopt the 

 converse process by searching the Patent Office and 

 other records, and producing what is called a mosaic 

 anticipation — one detail is shown in one jjatent, 

 another in a second, and so on. It has always seemed 

 to Sir John to be unfair that documents should be 

 evidence of anticipation ; evidence should be of prior 

 use, and the extent of that use should be sufficient 

 to prevent fraudulent evidence being accepted. The 

 object of a patent si>ecification is that the industn.- 



