September 1, 1899.] 



KNOWLEDGE. 



205 



a dull cirro-stratus cloak (il. Poey's PaUiuni) during a 

 storm. 



On the 2nd of .June, 1898, the writers were enabled 

 to secure the photograph of the rainbow shown in 

 Fig. 7. Exposure -- -Jg second. Diaphragm on the 

 Derogy objective - j'^. It will be seen that the bow 

 produced on the negative the effect of a luminous arch 

 projected on darker background. It was obviously the 

 shorter waves which proved the most efiicient in the im- 

 pression of the meteor. The bow can be traced in the 

 reproduction down to the landscape, especially in front of 

 a row of poplar trees bordering the right bank of the Seine. 

 The altitude of the sun at the moment being some twenty- 

 one degrees, the top of the arch was raised some twenty 

 degrees only above the horizon. 



The photograph is interesting as showing the inner 

 space of the bow to be much brighter than the outer, an 

 appearance which is not always noticeable to the eye. This 

 is due to the fact that whereas no light is sent to the 

 observer from the back of the drops situated outside the 

 first, and as far as the secondary bow, the drops inside 

 the primary do reflect light from their back, which in spite 

 of its enfeeblement through divergence, suffices to vaguely 

 illumine the inner segment. This is the region of the 

 " supernumerary bows " imesplained by Descartes and 

 Newton, but to which the illustrious Thomas Young, with 

 the intuition of genius, applied bis discovery of the law of 

 interference of light. The condition necessary for the 

 appearance of the supernumeraries is that the drops shall 

 all be of nearly equal sizes. Otherwise, as in the case of 

 the photograph, we have a confused superposition of the 

 various colours, which are thus blended into white light. 



Urttrrs. 



[The Editors do not hold themselves responsible for the opinions or 

 statements of correspondents.] 



THE RESOURCES OF THE SE.i, 

 To the Editors of Knowledge. 



Sirs, — I notice in your issue of .July 1st a somewhat 

 guarded review of Prof. Mcintosh's new work on " The 

 Resources of the Sea." 



The points at issue between the author and the Scottish 

 Fishery Board are, though interesting in themselves, of 

 minor importance compared with the opinion freely ex- 

 pressed in several places throughout the work, namely 

 that no restrictions should be placed on any method 

 employed or any area of our sea fisheries. Thus, at 

 p. 228, the author says ; — 



" So little can be done by man in the way of altering 

 Nature's laws in the sea that it might be more prudent to 

 leave the adjustment of the supply and the demand in her 

 hands." 



Again, at p. 231, he writes ; — 



" Yet so far as history and so far as observation at the 

 present time go there is no ground for alarm in regard to 

 the permanence of the food fishes." 



The matter is put more specifically on p. 229 : — 



" The grave and permanent deterioration of our in-shore 

 and off-shore fisheries has been dealt with in the foregoing 

 pages, and by a practical and unbiassed examination of 

 the areas themselves and of the statistics of fishes caught 

 in them, the condition is shown to be one that inspires 

 confidence and not alarm." 



Permit me then to point out. Sirs, what those statistics 

 consist of. They are records of certain hauls of the trawl 

 net, by various vessels of greatly varying tonnage, extending 



over periods varying from ten to two years, made in certain 

 closed areas around the Scotch coast. When practical 

 men are told that in certain tables — " barren hauls are 

 omitted" (p. 101), that trawls with bea"ms varying from 

 ten to fifty feet, with nets of varying mesh were used, 

 and that the trawling was •' for the most part carried on 

 by daylight " (p. 105), such statistics will be appreciated 

 at their true value. 



But, Sirs, the records of the fish markets and the news- 

 papers are and have proved conclusively that the fishing 

 grounds around our coasts are no longer producing our fish 

 food supply, and are indeed depleted ; and, further, that our 

 trawlers are now busy at the same work in Icelandic and 

 Biscayan waters, despite the strenuous opposition of the 

 coast authorities. 



The author does not deny this, for, at p. 9.5, he writes : — ■ 



" To commence with the most northerly, viz., Aberdeen, 



at which trawling has made great progress since the 



former date (1884), it is found that, whereas the chief 



supplies were brought fresh from the adjoining sea by the 



older paddle ships, or from the ^loray Firth by the more 



powerful vessels, much of the supply of the present day 



comes from the Great Fisher Bank or from Iceland." 



Again, speaking of the Government returns, he says :^ 



" While, therefore, the present statistics show no serious 



diminution, it may be truly said that the total is kept up 



only by supplies from Iceland, Faroe, and the Great 



Fisher Bank." 



Surely, Sir, no " scientific observer ' such as described 

 on p. 223, of whom it is said " the welfare of the 

 fisheries as a whole is his aim," can look on, while Hewitt's 

 Short Blue Fleet is shut down because the North Sea 

 grounds no longer yield a profit, and the British steam 

 trawler is daily seized and fined for fishing in -Danish 

 territorial waters, without drawing some practical conclusion 

 therefrom. Men do not abandon large and old established 

 businesses, or run the risk of getting hundreds of pounds 

 worth of goods confiscated without some reason ; and that 

 reason is plain to the intellect of even the unscientific, 

 namely, that the fish in the old fishing areas are no longer 

 caught profitably. This means to us : — 



1. That another food stuff has to be brought from 

 abroad ; 



2. That thousands of hard-working fisher folk are 

 being ruined ; 



3. That the fishermen-seamen counted upon by our 

 experts to help man the Navy, are being reduced in numbers 

 by leaps and bounds. 



One can only hope that this cleverly written book by 

 one of our highest authorities, with its bald and uncon- 

 vincing conclusions, wUl not tend to delay still further the 

 reform of our fisheries imtil it is too late. 



Charles S. Patterson, m.b., m.r.c.s., f.z.s., 

 Hon. Sec. British Sea Anglers' Society. 



THE SUN'S RADIANT HEAT. 

 To the Editors of Knowledge. 



Slrs, — A point touched on by your reviewer seems to me 

 worth discussing on its own account, and I hope some of 

 your able correspondents will be able to throw light upon 

 it. For my own part I have not adopted any theory on 

 the subject. The question is this, What becomes of the 

 radiant heat of the sun ? 



According to the ordinary view the sun is constantly 

 radiating heat in all directions, and, I think, it is generally 

 supposed that it is only a small portion of this heat that 

 encounters material bodies at any distance however great. 

 If so, the question arises what becomes of the residue? 



