Sept. 20, 1883J 



NATURE 



489 



causes of movements of the earth's crust ; for if the fluid or 

 viscous layer is chiefly due to internal heat and the relaxation of 

 pressure near the surface, it may exist much nearer to our feet 

 than could other a ise be admitted. 



One of the gravest difficulties that the theory that added 

 weight produces subsidence by acting on a fluid layer has had 

 to contend with has been the great depth at which this fluid 

 layer has had to be placed. It has always seemed to me next to 

 impossible that liquid lava could well up from any such depths as 

 t ose assigned to the viscous layer, or that a solid crust of so 

 great a thickness should be sensitive to, as it is now shown to be, 

 and rise and fall under, barometric changes. In acknowledging 

 Mr. Fisher's letter and thanking him, 1 feel I am ungrateful in 

 questioning that part of his work which interposes barriers which 

 would break up the continuity of the viscous layer; I allude 10 

 his theory of " the roots of mountains." There does seem to me 

 to be little fact in support of so startling a proposition, and I 

 think the existence of volcanic vents, scattered through and in 

 the midst of some of the highest chains, renders its acceptance 

 difficult. 



Mr. Murray restates his theory of the formation of coral at ills 

 and reefs in the clearest manner, but I do not see that he 

 explains any fact left unexplained by Darwin, or exposes any 

 flaw in I 'arwin's reasoning. These masses of coral may have 

 been continuously forming throughout even successive geological 



I BALLYCALLEY HEAD 



Sheet 21. Geological Survey of Ireland, Antrim Coast, facing north-east. 



periods, and their thickness is p rhaps not exceptionally remark- 

 able relative to that of slowly deposited oceanic sediments. 

 There isnoevidei.ee that atolls are mere incrustation- of volcanic 

 craters, and it seems to me difficult to imagine so great a number 

 of craters at the same level so completely masked. There are 

 volcanic i-les in abundance outside coral areas, but none I think, 

 or few, of the form of a coral atoll. After all, Mr. Murray only 

 shows that a second explanation is pos-ible, though I still prefer 

 the first. 



I regret, being from home, that I am unable to answer Mr. 

 Stanley. I may have alluded to the sinking of Greenland my- 

 self, and if I did not it was because the illustration was too 

 familiar and self-evident. The sinking on the Greenland coast 

 is not, I have understood, universal. 



I still think it would render a service to science if readers of 

 Nature residing on sea-coasts would furnish authentic examples 

 of elevation or subsidence or of waste. The magnificent Antrim 

 coast, which I have recently visited, furnishes examples of sub- 

 sidence among most unyielding rocks. The cliffs on the main- 

 land are capped with basalt and dip inland, yet the basalt 

 reappears in the Skerries out to sea with the same dip and at a 

 much lower level. The same correspondence in stratification is 

 seen between the mainland and Kathlin, but also with a great 

 difference in elevation. The dip inland in all cases on this coast 



should bring up much older rocks out to sea, unless we are pre- 

 pared to admit a fault running parallel to the coast, and follow- 

 ing its sinuosities, and at right angles to the general lines of 

 faulting. 



The way in which all the strata forming the cliffs along the 

 Antrim coast dip inland is very remarkable. The accompanying 

 tracing from the Geological Survey Map is of a particularly in- 

 dented coast-line, and the arrows show that the dip is every- 

 where away from the sen, irrespective of any general strike. In 

 fact the general strike mu-t often be the revere of that shown 

 on the coast for the same strata crop out at much higher levels 

 on the hills farther inland. I recollect that most cliffs that I 

 have examined, particularly in Hampshire, dip away from the 

 sea. It would appear that the removal of weight along a cliff 

 line causes a local elevation, which gives a cant inward, whilst 

 sub-idence takes place under sediment farther out to sea. This 

 seems to explain the observed facts connected with marine de- 

 nudation ; but 1 must take a future opportunity of entering more 

 thoroughly into this part of the question. 



Glasgow, September 12 J. Starkie Gardner 



" Zoology at the Fisheries Exhibition " 



Letters have been published in Nature of August 9 and 16 

 (pp. 334 and 366) by Mr. Bryce-Wright of Regent Street and 

 Prof. Honeyuian of Canada, calling in question the accuracy of 

 statements made in an article in Nature (vol. xxviii. p. 289) 

 which were condemnatory of exhibits for which these two 

 gentlemen are respectively responsible. It is natural that they 

 should seek to remove the unfavourable impression which the 

 statements in question were intended to convey : they seem, how- 

 ever, to have been unacquainted with the complete character of 

 the information upon which the statements were based. Mr. 

 Bryce-Wright states that it is not the fact that some of the corals 

 exhibited in Lady Brassey's case belong to him. Nevertheless 

 it is the fact that when the jury of Class V. asked Mr. 

 Bryce-Wright to point out the corals entered in the offi- 

 cial catalogue under his name, No. "813/'," he informed 

 them that the corals so entered were in the same case with Lady 

 Brassey's corals, and formed part of that collection. It is also 

 the fact that in the opinion of experts the names attached by 

 Mr. Bryce-Wright to many of these corals are incorrect ; and as 

 to his assertion that thee specimens have been compared with 

 those in the Biiti-h Museum and with tho-e obtained during the 

 Challenger Expedition, it is a fact that neither the one series nor 

 the other has been accessible for such purposes for some con- 

 siderable time, and I have reason to believe that no qualified 

 zoologist has made a comparison of the coral, exhibited by Lady 

 Brassey and Mr. Bryce-Wright with any collection at all. 



Ihe letter of Prof. Honeyman in reference to the naming and 

 state of preservation of the Collection in the Canadian Depart- 

 ment, tor which he is responsible, is misleading. The discredit- 

 able state of that collection, to which a passing allusion only was 

 made in NATURE, has been remedied in one or two instances 

 since the visit of the jury of Class V. Should there be any 

 doubt as to the justice of the opinion expressed in the article in 

 Nature, I would simply ask Prof. Honeyman whether he 

 would have any objection to allowing the matter to be decided 

 by reference to the report of the jury of Class V., of which he 

 was a member. I should be surprised (and so I think would he) 

 were the repor' of that jury, when published, found to be at 

 variance with the opinion expressed in the article in NATURE. 

 Prof. Honeyman 's statement that the specimen of Cryptochiton 

 Stellcri is properly exhibited in a convenient glass jar and labelled 

 inside and out, is calculated to mislead. When first exhibited it 

 was n .t labelled with any name ; subsequen'ly it was labelled 

 with the name of a genus of Holothurians, " Psolus." After the 

 visit of the jury of Class V., probably as the re ult of informa- 

 tion imparted by some of the eminent zoologists who served on 

 that jury, it was labelled with its proper name. Without citing 

 details, I shall simply stale that there are (or were when the 

 article in Nature was written) far more serious blunders in the 

 identification of specimens and worse instances of bad preserva- 

 tion in the Canadian collection of Invertebrata than those to 

 which special allusion has been made. 



The Writer of the Article 



A Complete Solar Rainbow 



Mr. D. Morris, in his account of this rainbow (p. 436) ap- 

 pears to have fallen into a mistake in stating that its inner dia- 



