214 



NA JURE 



\yan. 3, i8i-'4 



prevalence of prairie fires in spring and autumn. Personally I 

 favour the latter, though both causes may in part he answer- 

 able. If worms abound in Iceland (65° N. lat.), in Ker- 

 guelen Land (50° S. lat.), and in Toronto (43 '4° N. lat., 

 mean winter temperature 275° ¥.), why should they not also 

 occur at Winnipeg (50' N. lat.)? Certainly the mean winter 

 temperature is very low, being about 8° F., and the mean 

 minimum for eleven years — 4oJ° F. I made special inquiries 

 as to the depth to which the soil in Manitoba becomes fiozen 

 in winter. This is often as much as five or six feet, but only, 

 I believe, in the more exposed places, and certainly as a 

 rule it is thawed again in the spring. I do not think this would 

 render the ground uninhabitable by w orms when they are able to 

 exist in Iceland. Mr. Darwin says nothing as to the effect of 

 frost on worms except (p. 26) that "worms are sensitive to a 

 low temperature, as may be inferred from their not coming out 

 of their burrows during a frost"; but he states (p. no) that 

 they are easily able to descend three or four or even seven or 

 €ight feet below the surface. It would be interesting to ascer- 

 tain whether worms inhabit equally cold portions of the Old 

 World. 



But the agency which I believe has caused the absence of 

 earthworms from the North- West is, as already stated, the 

 prairie fires which annually sweep over enormous portions of 

 the country, totally consuming the grass, and converting it into 

 a black ash. This, it might well be imagined, would for months 

 together completely deprive any worms that formerly existed of 

 that variety of decaying vegetable matter that composes their 

 food ; and assuming that fires have annually passed over large 

 portions of the prairies for scores of generations (as seems in 

 every way probable), it appears to me only reasonable to sup- 

 pose that this cause would effectually have exterminated the 

 worms from the country or have prevented them occupying it. 

 It is my belief (as I shall elsewhere state more fully) that the 

 very fertile, fine, black, powdery, and almost soot-like soil from 

 one to three feet thick, even the open, treeless natui'e of the 

 prairies themselves, and the absence from their surface, so far as 

 my observation goes, of every single species of moUusk, while 

 many species abound in all the ponds, lakes, and streams, ore all 

 in a large degree, if not entirely, due to the action of the fire. If 

 this view ultimately turns out to be correct, it will be further 

 seen that the very means which has deprived the soil of the 

 North-West of that natural cultivation which the soils of most 

 other countries enjoy has, at the same time, liberally supplied it 

 with a manure resulting from the charred ashes of the grass 

 which is annually burned. My friend, Mr. T. Rogers, who has 

 taken much interest in the absence of worms from the North- 

 West, and is inclined to attribute it rather to frost than to fire, 

 though he suggests that the "alkali "may possiljly have had 

 something to do with it, has already brought the subject before 

 the Literary and Scientific Society of Manchester, where he seems 

 to have met with a good deal of incredulity. 



As anothei' evidence of the absence of worms, the numerous, 

 large. Glacial boulders that strew the prairie ■; around Brandon 

 and elscAvhere may be cited. These, had worms exi-ted, would 

 doubtless have long ago been lowered beneath the surface, as 

 also the skulls and other bones of buffaloes, which so abound on 

 ;the prairies, and most of which have evidently lain there a long 

 -while. Nevertheless some of these have been buried in the course 

 of time, as one gentleman told me that he had sometimes turned 

 them up from a depth of two or three inches beneath the surface 

 when ploughing. Their burial may have been accomplished by 

 the wind drifting soil over theiri, or by the working of gophers. 

 Of these peculiar little animals two species are very abundant 

 •on the prairies, where they make extensive burrows, which it 

 seems possible may to some extent accomplish the natural cnli- 

 vation of the soil in the way Avornis are accustomed to do it 

 elsewhere. Some more suggestive remarks on this point may 

 be found in a paper by Mr. .Seton, published in the Report of 

 ithe Manitoba Department of Agriculture for 1S82, and which 

 may I'e studied with advantage. RoBT. Miller Chuisty 

 Chignal St. James, near Chelmsford, December 20, 1S83 



Magnetic Dip in South China and Formosa 



While engaged on a meteorological mission in China I 

 availed myself of the opportunity to make the following deter- 

 minations of the magnetic dip. The observations in Hong Kong 

 were made at the public gardens, the Ob ervatory being not yet 



ready. On October to I observed at the British Consulate ; on 

 November 3 at ihe English Presbyterian Missions Compound, 

 Swatow. In Amoy I observed at the residence of the Commis- 

 missioner I.M. Customs, in Takow (Formosa) at the Custom 

 House, and at the South Cape (Formosa), near the magnificent 

 fortified lighthouse. It is to be feared that the observitions on 

 the coast of China are slightly vitiated from local attraction, the 

 rocks consisting of ferruginous granite. Southern Ferposa is 

 built up of coral, raised in places to a great height, no doubt 

 through volcanic action. Slight earthquakes are of common 

 occurrence in Formosa, whereas along the coast of China they 

 are rare and of no importance except to the seismologist. 



Place 



Da 



Local M.T. 



Dip, 



Hong Kong ... 1S83, Nov. 5 ... 5 g p.m. ... 32 17 



• •■ ,, ,, 9 •■■ 5 4 .. •■■ 32 19 



Swatow ,, Oct. 10 ... 5 24 ,, ... 34 23 



,, Nov. 3 ... II 25 a.m. ... 34 17 



Amoy ,, Oct. 14 ... 3 50 p.m. ... 36 45 



., >, 16 ... 5 10 ,, ... 36 50 



Takow ,, ,, 24 ... 2 45 ,, ... 32 54 



South Cape ... ,, ,, 27 ... 40,, ... 31 24 



... „ ,, 28 ... 4 30 ,, ... 31 27-5 



... ,, ,, 29 ... 3 20 „ ... 31 24-5 

 W. DOBERCK, 

 Hong Kong, Nov. 10 Government Astronomer 



THE ORIGIN OF CORAL REEFS 

 Ty EGARDING this interesting geological problem, 

 -l- »- which has recently beeii discussed in N-fVlURE, we 

 are enabled through the kindness of Mr. Murray, of the 

 Challciii^cr Commission, to publish a letter which has 

 been addressed to him by Dr. Guppy from the Pacific. 

 The importance of this communication will be recognised 

 in the confirmation it supplies of the inference that coral 

 reefs start upon a platform of limestone composed of the 

 remains of foraminifera, &c., and are themselves of no 

 great thickness. Dr. Guppy will no doubt continue his 

 researches, and we may hope to obtain from him precise 

 data regarding the average thickness of the coral rock, 

 the lithological difference between it and the underlying 

 limestone, the structure of the limestone, whether any 

 succession of organisms can be detected in it, and 

 whether at any point the underlying volcanic rock can be 

 seen which would afford a measurement of the thickness 

 of the calcareous deposits. The effects of denudation 

 and their relation to height above the sea will no doubt 

 also receive his attention. 



" Sliortlands Islands, Solomon Group, 

 ^^ August 7, 1883 



" During the twelve months I have spent in this group of 

 islands — serving as surgeon on board H.M. sunxying-ship 

 Lark — I have been tiiuch interested in and have devoted 

 considerable attention to the raised coral formations in 

 various islands ; and as my observations may be of 

 service towards confirming the views which you have 

 advanced with reference to coral islands and reefs, I will 

 state briefly the results of my observations. 



"Excluding the large continental islands, I will refer 

 for the sake of brevity to the numerous small islands of 

 this archipelago, those of volcanic, and those of cal- 

 careous formations. Confining myself to the islands of 

 calcareous formation, I will pass over the numerous small 

 islands which are entirely comi^osed of coral detritus, 

 sand, and shells, and have been formed by the materials 

 thrown up by the waves at the present sea-level ; and 

 will restrict niy remarks to a very common t_\ pe of islands 

 in this group, with gently sloping and rounded profile, 

 having an elevation varying perhaps between 100 and 1 100 

 or 1200 feet, and composed in bulk of an impure earthy o> 

 argillaceous limestone', usually bedded, and almost alwajs 

 foraininiferous, now and then rich in other pelagic 

 organisms, such as Pteropods. On this rock rests the 



