128 



NA TURE 



[Dec. 9, 1886 



lake is a great depth, so that this hill of 200 feet or more 

 rising from the bottom represents a vast amount of solid 

 matter, to say nothing of the thick deposits of dust all 

 over the island. The lake was still bubbling in places, 

 and things are b\' no means settled down yet. At Vax'au, 

 where we touched two days ago, they had just had a very 

 severe earthquake, and shocks are still going on at iN iua- 

 foou (vertical, / wds told, but my informant's wits were 

 much shaken by recent" events) daily on the level ground 

 near our landing-place, from which it is inferred that the 

 danger is not over. Strong gases too are perceptible 

 rising from the ground near the coast, which is always 

 where they apprehend most danger, and an outburst 

 of lava. i suppose the solid matter coming up through 

 the deep lake is pulverised into the (to life) comparatively 

 harmless dust. During the earthquake of August 12, the 

 captain of a ship at anchor found that, whereas he had 

 paid out twenty fathoms of chain over-night, he had only 

 eight fathoms under him in the morning. I never saw 

 such big coco-nuts anywhere, though the trees are not e.K- 

 ceptionally big, indeed there seem to be no very fine or 

 old trees of any kind on the island, which favours the 

 theory of a modern origin, for the soil is very fertile. The 

 name means New Niua, the Old Niua being probably the 

 neighbouring Keppel Island or Niua-tobu-dabu. I wish 

 I could give you a better or fuller and more interesting 

 account of the whole afl'air, but the visit was a very 

 hurried one, and, in fact, I had not more than two hours 

 on shore. Still it may interest you, as it is written on the 

 very spot: no other account is likely to reach England. 

 I send a pinch of 'sand' from the crater. " C. T." 



This " sand " or " dust " is a very dark-brown— almost 

 black — colour. When examined with a lens it seems com- 

 posed mainly of fragments of glass, and has a slightly 

 speckled aspect; owing to the mixture of lighter and darker 

 fragments ; one or two glassy-white fragments may also be 

 noted. When some of the dust is placed under the 

 microscope, it is seen to consist almost wholly of frag- 

 ments — some rudely polygonal in shape, others flattish 

 chips — of a brown glass ; the former being the commoner. 

 The majority of the bits vary from about 'Ol inch to 

 ■03 inch in diameter, and the latter measurement is but 

 rarely exceeded. Minute chips are also present, but they 

 do not form at all an important constituent in the mass. 

 A conspicuous characteristic is the (apparently) entire 

 absence of the tiny pellets of " cindery " scoria, so frequent 

 a constituent of volcanic dust, and of the fine pulverulent 

 material, the presence of which commonly makes it need- 

 ful to mount the dust on a slide before it can be properly 

 studied. I have found no difficulty in examining this 

 Niua-fu dust, and even the finer chips — often less than 

 'ooi inch in diameter — by simply spreading it over a sheet 

 of glass. The glass fragments, even when very minute, 

 have a tinge of brown : when about 'oi inch in thickness, 

 they are fairly translucent, and a rich olive-brown in colour ; 

 but as they approach '03 inch in thickness they become 

 opaque, light only passing through the thinner edges. 

 Small cavities, spherical, or egg-shaped, are not infrequent, 

 but the glass is remarkably free from microlithic in- 

 closures. No granulation of the colouring-matter is per- 

 ceptible, as a rule, with a magnification of 150 diameters ; 

 opacite dust and trichites (especially the latter) are very 

 rare ; and of other microlithic inclosures I ha\-e only 

 seen an occasional lath-shaped crystallite (.-' feldspar). I 

 have not identified among the fragments either biotite, 

 augite, or hornblende ; so that if any of these minerals 

 are present they must be very rare. The clear glassj- 

 fragments mentioned above are feldspar — probably labra- 

 dorite. They do not in number exceed about 2 or 3 per 

 cent, of the whole. INIany of the flatter brown-glass 

 fragments exhibit ropy folds or the remains of a cellular 

 structure, evidencing that they are due to the destruction 

 of a very vesicular glass, while the more solid polygonal 



fragments may be the detritus of the thicker parts of the 

 same or of a more uniform glass. The strong brown 

 colour of the fragments reminds me of specimens of the 

 more glassy lavas of the Sandwich Islands in my collec- 

 tion ; and like them I should, from microscopic examina- 

 tion, consider the rock a basalt-glass (tachylyte) with a 

 silica percentage, which was probably above rather than 

 below 50. This view accords, I find, with Cohen's state- 

 ment concerning the lava of Niua-fu, which, judging from 

 his description, is very similar to that above described 

 {Neites Jahrh.fur Min. 18S0, vol. ii. pp. 36 and 41) ; he 

 says that it is almost identical in composition with the 

 " basalt-obsidians " {i.e. tachylytes) of the Sandwich 

 Islands. It contains 5074 of silica; their analyses 

 show from 50'82 to 53'8l. 



While the above was passing through the press, I 

 received from my friend Dr. S. Rideal a determination of 

 the specific gravity of the volcanic material (powdered to 

 get rid of cavities). The specific gravity is 2 726. As the 

 feldspar is included, and it is slightly the lighter, the 

 specific gravity of the glass itself must be a little higher, 

 about 273. Hence we need not hesitate to call it a 

 tachylyte. The average of six Sandwich Island glasses 

 is 271 (see Judd, O.J. G. S., xxxix. 444). 



T. G. BONNEY 



FOURTH ANNUAL REPORT OF THE FISHER Y 

 BOARD FOR SCOTLAND 



THE Report of the Fishery Board for Scotland in- 

 creases each year, not only in size, but in interest for 

 the general public, as well as for those readers whom it 

 specially concerns ; and, unhke ordinary Blue-books, its 

 pages are to a large extent devoted to scientific papers 

 which appeal to many not directly concerned with the 

 fishery industry. 



The herring-fisheries continue to be most productive. 

 A very striking feature of the summer herring-fishery of 

 1885 is, that many in-shore grounds, where herrings 

 were previously found in great abundance, but which 

 had recently been all but deserted, were restored 

 to their former fertility. The increase of the herring- 

 fishery in the Shetland district, which now ranks as the 

 most important in the country, still continues, greatly to 

 the improvement of the condition both of the people and 

 of their boats. The fish are of finer quality than those 

 taken on other parts of the east coast. The takes of 

 other sea fish and salmon were also very large. The 

 gross total estimated value of the sea and salmon-fisheries 

 for Scotland was 2,859,822/. I5j>-. The Board have already 

 expressed their regret that so many tons of sprats are 

 annually used as manure. Could they be transmitted to 

 populous districts at a reasonable rate, they would be a 

 cheap and valuable addition to the food-supply, or, where 

 this was impracticable, preserved as anchovies as in 

 Norway, or as sardines as in Canada. The importance 

 of utilising the by-products of the fisheries is now widely 

 recognised. Papers by Dr. Stirling and Mr. Haliburton 

 give an account of certain economical products obtained 

 from fish, and experiments are being made on a fairly 

 large scale by Mr. Sahlstrom at Aberdeen, which may, it 

 is hoped, lead to some practical results. Investigations 

 on whitebait by Prof. Ewart and Mr. Matthews showed 

 it to consist almost entirely, and at all seasons, of young 

 sprats and young herrings, varying according to the sea- 

 son of the year and the place of capture. It might, 

 therefore, be advantageous for the Firth of Forth and 

 other in-shore waters to send supplies of whitebait to the 

 English markets. 



The Scientific Committee of the Board had the assist- 

 ance of Mr. Brook, Prof. Stirling, and Mr. Duncan 

 Matthews, of Aberdeen ; Prof. Mcintosh, of St. Andrews ; 

 Prof. Greenfield and Dr. Gibson, University of Edin- 



Ii 



