440 



NATURE 



{^August 2 2, 1878 



We accordingly confine ourselves to the mere mention of it by 

 way of suggestion. 



Third Report of the Covimittee, consisting 0/ Dr. Joule, Frof. 

 Sir W. Thomson, Prof. Tait, Prof. Balfour Stewart, and Prof 

 Maxivelljor the Determination of the Mechanical Equivalent of 

 Heat. — Dr. Joule has published a paper giving in extenso the expe- 

 riments summarised in the last two reports, in the Philosophical 

 Transactions of the Royal Society, where was published his 

 former paper in 1850. The new result which confirms the old 

 one, gives 772*55 foot pounds as the equivalent at the sea-level, 

 and the latitude of Greenvdch of the heat which can raise a 

 pound of water, weighed in vacuo, from 60° to 61° F. of the 

 mercurial thermometer where the permanent freezing point is 

 called 32°, and the permanent boiling point of water under a 

 barometrical pressure of 30 inches of mercury raised to 60° F. 

 is 212°. The work at present in hand is a more accurate 

 investigation of the true position of the freezing and boiling 

 points of the thermometer when cleared from the effects of the 

 imperfect elasticity of the glass of which they are constructed. 

 The correction to the above equivalent which may thus accrue, 

 is not expected to be of considerable amount. 



Report of the Committee appointed for the purpose of inquiring 

 into the possibility of establishing a '* Close Time" for Indigenous 

 Animals. — The Committee being dissatisfied with certain points 

 in the Report of the Scottish Fishery Commissioners, addressed 

 a letter to the Home Secretary, calling attention to the following 

 points : — 



"I. That conclusions Nos. 2 and 3 of the Commissioners, 

 viz., that ' Legislation in past periods has had no appreciable 

 effect,' and that 'Nothing that man has yet done, and nothing 

 that man is likely to do, has diminished, or is likely to diminish, 

 the general stock of herrings in the sea,' if correct, are absolutely 

 contradicted by conclusion No. 13, which recommends that 

 'The Sea-Birds Preservation Act, protecting gannets and other 

 predaceous birds which cause a vast annual destruction of 

 herrings, should be repealed in so far as it applies to Scotland.' 



" II. That conclusion No. I, stating that * The herring-fishery 

 on the coast of Scotland as a whole has increased and is in- 

 creasing,' clearly shows that there can be no necessity for the 

 step recommended in conclusion No. 13 as above cited. 



" III. That conclusion No. 13 seems to have been arrived at 

 from exaggerated or incorrect information, as will appear from 

 the following considerations : — The number of gannets on Ailsa 

 is estimated (' Report,' p. xi.) at 10,000, and a yearly consump- 

 tion of 21,600,000 herrings is assigned to them; while the 

 . Commissioners assume that there are ' 50 gannets in the rest of 

 Scotland for every one on Alisa,' and on that asstmiption 

 declare that the total destruction of herrings by Scottish gannets 

 is more than 1,110,000,000 per annum. This is evidently a 

 miscalculation ; for, on the premises, this last number should 

 be 1,101,600,000, a difference of more than 8,000,000. 



" But, more than this, supposing the figiu^es at the outset are 

 right, it appears to the Close-Time Committee that the succeed- 

 ing assumption of the Commissioners must be altogether wrong ; 

 at any rate, there is no evidence adduced in its support, and 

 some that is contradictory of it. 



" The number of breeding-places of the gannet in the Scottish 

 seas has long been known to be five only, as, indeed, is admitted 

 by one of the Commissioners (Appendix No. 2, p. 171 ; and the 

 evidence of Capt. M 'Donald, which is quoted in a note to the 

 same passage, while estimating the Ailsa gannets at 12,000 in 

 1869 (not 1859, as printed), puts the whole number of Scottish 

 gannets at 324,000 instead of 510,000, which there would be at 

 the rate of 50 in the rest of Scotland for one on Ailsa, according 

 to the Commissioners' assumption. 



" Moreover, 50,000 of these 324,000 birds, or nearly "one- 

 sixth, are admitted by this same Commissioner to be ' of great 

 value to the inhabitants' of St. Kilda, and, indeed, they are of 

 far greater value to them than any number of herrings, since it 

 is perfectly well known that the people of St. Kilda could hardly 

 Eve without their birds ; therefore this 50,000 must be omitted 

 from any estimate of detriment. • Deducting, then, 50,000 from 

 Capt. M'Donald's 324,000, we have 274,000, and these, at the 

 Commissioner's estimate, would consume 600,060,000 herrings 

 instead of the 1,110,000,000 alleged by the report, and, there- 

 fore, nearly 200,000,000 fewer than the Commissioners' estimate 

 of the annual take of the Scottish fisheries (800,000,000)— 25 per 

 cent, less instead of 37 per cent. more. 

 ■ "Hitherto the supposition of the report, that the gannets 



frequent the Scottish seas all the year round, has been followed ; 

 but the Close-Time Committee begs leave to observe that, as a 

 matter of fact, these birds are not there in force for more than 

 half the year. 



" This, then, will require another abatement to be made. 

 Not to exaggerate the case, the Committee assumes them to 

 frequent these waters seven months, or seven-twelfths of a year. 

 This will make their annual capture of herrings 350,350,000, 

 instead of the more than 1,110,000,000 of the Commissioners, 

 being nearly 700,000,000, or much less than one-third, fewer. 



" ^Y* .^^^t ^° ^11 the evidence received and published by the 

 Commissioners only two witnesses allege that any harm has re- 

 sulted to the fisheries from the Sea-Birds Protection Act. Of 

 these, the first, Robert M'Connell, presented a petition from 

 the fishermen of Girvan, in which it is stated (p. 145) that ' no 

 legislation is called for or required ; ' while another witness 

 from the same place, John Melville (a fishery officer), declares 

 (at p. 146) that ' The fishery has very much increased this last 

 year. Recent years have also shown a gradual increase. The 

 increase is partly due to the increased machinery and partly to 

 the increase in the number of herrings.' 



"The second witness unfavourable to the Act, John M 'William 

 (an Inspector of Poor), speaks (pp. 147-49) o^V from personal 

 knowledge acquired between 1833 and 1853, when he ceased to 

 be a fisherman, and not from any recent experience. He can 

 therefore scarcely be held competent to give an opinion of his 

 own as to whether the Sea Birds Protection Act (passed in 1869) 

 has injured the fisheries. Another witness recommends the re- 

 peal of this Act ; but he, Hugh MacLachlan, expressly states 

 (p. 143) that he ' thinks the cause of the decrease [in the 

 numbers of herrings taken] is the catching immature fish ; ' and 

 the remedy he proposes is the adoption of a strict Close Time. 



"V. That, on the other hand, the utility of sea-birds in 

 pointing out the situation of shoals of herrings and other fish is 

 not only generally notorious, but is even admitted in the Report 

 (pp. 57 and 175). 



"VI. That if the Sea-Birds Act be repealed on the grounds 

 alleged for Scotland, its repeal for England and Ireland must 

 logically follow ; and this Committee trusts that no steps may 

 be taken to repeal the Act for Scotland." 



In view of any proceedings which may be taken in the Session 

 of 1879 in regard to the recommendations of the Scottish 

 Herring-Fishery Commissioners, as well as on general grounds, 

 the Committee urges its reappointment. 



SECTION A. — Mathematical and Physical. 



Note on the Pedetic Action of Soap, by Prof. W. Stanley 

 Jevons. — Since the publication in the Quarterly Journal of 

 Science for April, 1878, of my paper on Pedesis, or the so-called 

 Brownian movement of microscopic particles, it has been 

 suggested to me that soap vrould form a good critical substance 

 for experiment in relation to this phenomenon. It is the opinion 

 of Prof. Barrett, and some other physicists, that the movement 

 is due to surface tension, whereas, I believe that chemical and 

 electromotive actions can alone explain the long-continued and 

 extraordinary motions exhibited by minute particles of almost all 

 substances under proper conditions. Soap considerably reduces 

 the tension of water in which it is dissolved, without much 

 affecting (as is said) its electric conductibility. If, then, pedesis 

 be due to surface-tension, ;we should expect the motion to be 

 killed, or much lessened when soap is added to water. 



Having tried the experiment, I find that the result is of the 

 opposite character to what Prof. Barrett anticipated. With a 

 solution of common soap the pedetic motion becomes consider- 

 ably more marked than before. I have observed this result not 

 only with china clay and some other silicates, but also with such 

 comparatively inert substances, as the red oxide of iron, chalk, and 

 even the heavy powder of barium carbonate. The last-named 

 substance, one of those which we should least expect to dance 

 about of its own accord, gave a beautiful exhibition of the move- 

 ment when mixed with a solution of about i per cent, of soap, 

 and viewed with a magnifying power of 500 or i,coo diameters. 



The correctness of this result was also tested by observing the 

 suspending power of solutions of soap-solution compared with 

 water. If a little china clay be diffused through common 

 impure water, that, for instance, of the London Water Com- 

 panies, the greater part of the clay will scon be seen to collect 

 together in small flocks and fall to the bottom in tvv-o or three 

 hours, the water being almost clear. However, if about I per 



