May 3, 1877] 



NA TURE 



7 



Alyn. Their origin is well indicated in these positions, by the 

 manner in which they lie opposite the mouths of the valleys at 

 right angles to the course of the presertt streams. 



The most remarkable of all these is a lonj; ridge running 

 parallel to the Great Western Railway near Gresford. It is 

 marked and shaded on the ordnance geological map. Bailey 

 Hill, Mold, is another. This is altiiliuted to the Danes — 

 described in the guide books as a Danish fortification. I have 

 proved the glacial origin of these mounds by finding in them 

 striated subangular boulders, that have travelled considerable 

 distances ; such, for example, as large blocks of the Llanarmon 

 limestone, and rounded lumps of curly cannel, that miist have 

 crossed the lidge of ihe Hope Mountain, the height of which 

 varies from yx> to Soo feet above the Leeswood and Tryddn 

 valleys from which the coal must have been carritd. On one 

 occasion, during the construction ot the Wrexham Mold and 

 Coniiah's Quay Railway, I saw a large fire blazing in a navvy's 

 shed, and upon e.xamination found that the fuel was curly 

 cannel they had found in making a cutting. They described 

 this find as two pieces, each one " bigger than a man's head." 

 I brought away an unbt;rnt fragment of about 2 lbs. weight. It 

 was a subangular corner, smoothed and faintly striated. The 

 nearest cannel seam to this place — which is over the millstone 

 grit — is about four miles, with the Hope Mountain intervening. 



A curious example of the unexpected bearings of scientific 

 investigations upon commercial interest was presented by these 

 cannel boulders. Two or three years before I commenced the 

 study of the ancient glaciation of this district, Mr. W. C. Hussey 

 Jones had proved the value of this curly cannel as a source of 

 paraffin, and what are called paraffin oils, &c. Great excitement 

 resulted, and a great rush was made to " the Flintshire oildorado." 

 This curly cannel was sold at prices varying from twenty-five shil- 

 lings to thirty shillings per ton at the pit's mouth, while the price of 

 ordinary main coal was only six shillings. The owners of this 

 cannel, or holders of leases or "taknote3,"givinga licence to w-ork 

 it, made large sums of money (as much as So,ooo/. was paid for the 

 transfer of one lease), and consequently great search was made 

 for new seams. Among the searchers were the farmers, land- 

 owners, and outside speculator;, who commenced boring and 

 sinking and foiming companies for cannel mining in the regii n 

 covered by these "hog wallows;" the evidence upon which 

 their expectations were based being the discovery of pieces of 

 cannel on or near the surface, turned up by the plough or other- 

 wise. Many thousands of pounds v.'ere thus wasted. One very 

 worthy man, that I knew very well— a hard-working Welsh 

 farmei — spent the savings of a whole life-time in searching 

 for cannel on his farm, where he had frequently turned up frag- 

 ments in ploughing. His death speedily followed his ruin. 

 There were many other similar cases. Had I commenced my 

 investigations three years sooner I might have explained the 

 strange and apparently incomprehensible anomaly of Leeswood 

 cannel being found on the south side of the Chester and Mold 

 Railway, and in the neighbourhood of Caergwrle, in spite of an 

 intervening ridge of mountain. 



One very curious and instructive feature of these mounds is 

 their change of shape as we proceed from the hUl slopes towards 

 the great plain known as the Vale Royal, which was formerly a 

 great estuary or fjord of the Dee. Instead of the long and 

 rather steep hogback ridges we now find a general outspreading 

 deposit dotted here and there rather sparsely with obtuse conical 

 mounds, so obtuse and so much disturbed by agricultural opera- 

 tions that they can only be detected by careful observation. 



My explanation of these differences is that the glacier which 

 planed the millstone grit of the Hope Mountain by sweeping 

 over and around it, originally spread out upon the waters cf the 

 estuary now forming the Vale Royal, and thus formed Ihe out- 

 spread deposit ; that it afterwards receded, and the icebergs that 

 broke off and floated away from it were stranded here and there, 

 thawed, deposited their contents, and thereby formed the 

 mounds ; while the oblong ridges mark the final step-by-step 

 recession and oscillations of the dying glacier, which formed 

 them partly as terminal moraines, and partly by ploughing up 

 and thrusting before it, in the course of its advancing oscilla- 

 tions, the previously deposited glacial drift. I throw out these 

 speculations suggestively, to be taken for what they are worih ; 

 they fit the facts well enough so far as I have been able to study 

 them, but the main object of this letter is to direct attention to 

 this and other corresponding deposits near at home that appear 

 to me to be worthy of further investigation, especially by resi- 

 dents in the neighbourhood and the members of local field- 

 clubs, &c. The Liverpool Naturalists' Field Club paid a visit to 



the district while I lived there, and I showed the geological 

 members some of these deposits. W. Mattieu Williams 

 Belmont, Twickenham, April 24 



It is appatent from Prof. Le Conte's description of the prairie 

 mounds (Nature, vol. xv. p. 530) that the drift mounds figured 

 and mtntioned by me (vol. xv. p. 379) have quite diflerent 

 origins. The prairie mound would seem to be somewhat similar 

 and have the same origin as a tussocky bog or mountain. The 

 lormation of a tussocky bog has been described in " Valleys and 

 their Relation to Fissures, &c.," p. 14. A tussocky mountain 

 is similarly formed very hot weather cracks the peaty up • r ^r.U 

 forming deep fissur^-s ; while subsequent weathering chan_ :.u . 

 portions between the fissure into small hil s. I lately saw en 

 the coast of Wicklow a considerable area of .-Eolian dnft of this 

 hummocky nature ; the hillocks being about four feet high. 

 They were so regular as to have the appearance of being moulded 

 from one model. These could not possibly have their origin in 

 fissures ; but they seemed to have a connection with bunches of 

 bent, round which the wind collected heaps of sand. But again 

 why should the bunches of this grass grow at regular intervals ? 

 In the same neighbourhood some of this .'Eolian drift is piled in 

 long parallel ridges, about five or six feet high, and having quite 

 an artificial look. These evidently are wind formed ; but how it 

 is hard to conjecture, as they run oblique to the prevailing and 

 most effective winds. G. II. Kinahan 



Ovoca, April 24 



Greenwich as a Meteorological Observatory 

 In Mr. Buchan's objections to the hypothesis that the tempera- 

 ture of Greenwich is raised by the proximity of London one 

 most important consideration has been omitted. Granted that 

 the mean temperature of the summer months, June to September, 

 is C'g higher at Greenwich than at the eight other stations re- 

 ferred to, it does not follow that this alone is the cause of the 

 higher average temperature at the former place. Greenwich 

 occupies a position farther from the Atlantic and nearer the 

 Continent than the majority of the selected stations, and we 

 might therefore expect to find it subject not only to a higher 

 temperature in summer, but also to a lower temperature in 

 winter. If this be so, the excess which Mr. Buchan admits may 

 be accounted for by the raising of the mean winter temperature 

 from artificial causes ; and this view of the case seem to be con- 

 firmed by observation. The station at Leyton, Essex, supplies 

 the requisite data ; for, although near London and rapidly in- 

 creasing in population, it is, or rather was, in a country district 

 when the observations were made. It is situated on the verge 

 of Epping Forest, is separated from London by the Hackney 

 Marshes, is rather more than 6| miles in a direct line from St. 

 Paul's Cathedral, from which Greenwich is 4i[ miles distant, and 

 is 7 miles nearly north of the last-mentionsd place. The meteoro- 

 logical observations were undertaken with the express intention 

 of comparing them with those at the Royal Observatory, with 

 which object the instruments were mounted on a stand precisely 

 similar to the Greenwich stand, and the exposure was unexcep- 

 tionable. The comparison relates to the daily maximum and 

 minimum temperatures for the three years ending November, 

 1863. The average was at Greenwich 5°^'4> -Leyton 49°'9. 

 Allowing for elevation, the results are : — 



These results prove that Greenwich is warmer than Leyton, 

 which is farther removed from the influence of London, and that 

 during the winter months the temperature is higher both by day 

 and night, but chiefly by night, when the excess is i°-3 ; also 

 that in summer, while the nights at Greenwich are warmer than 

 at Leyton, the days are cooler. The inference is that the artificial 



