Oct. 14, iSSoj 



NA TURE 



559 



no doubt that the southern coast of Florida affords exceptional 

 advantages for the successful study of the formation of coral 

 reefs. Joseph LeConte 



Berkeley, California, September l8_ 



Geological Climates 



' The dilemma into which Dr. Houghton thrusts the rigid 

 uniformitarian school is one which was enlarged upon some 

 years since, when reef-building corals were asserted, upon the 

 evidence afforded by fossils, to have existed during the Miocene 

 and Oligocene ages in seas where Tasmania now exists in the 

 south and Hampshire in the north. There are no instances of 

 large masses of reef -building corals in corresponding latitudes at 

 the present day, and the range of these surface-living, high- 

 temperature-requiring zoophytes is well known. 



Uniformitarians may take comfort, however, and slip under 

 the horns which Dr. Houghton so ably presents for their trans- 

 fixment. Where I now write, on the Bagshot sands and gravels 

 of Cooper's Hill, facing the cold north with a touch of the east, 

 there is a patch of bamboo canes in full leaf. They were in 

 full leaf at this time last year. The plant survived out of doors 

 the extreme frost and fogs of last winter and other evidences of 

 a temperate climate, and it has been in beautiful leaf all this 

 summer. 



Now everybody knows that in torrid India the bamboo grows. 

 Therefore if the palaeontologist of the year A.D. 18S00 should 

 dig up the Cooper's Hill stalks and leaves, and should have the 

 opportunity of examining in some future Kew the bamboos of 

 the hot parts of the earth, he would logically, geologically, 

 palseontologically, but somehow unreasonably, come to the con- 

 clusion that Cooper's Hill and India enjoyed corresponding and 

 intensely tropical climates in 18S0, during the geological age 

 when the earth's polar axis was certainly inclined nearly 234° to 

 the plane of the ecliptic. P. Martin Duncan 



Royal Engineering College, Cooper's Hill, Staines, October 9 



The Yang-tse, the Yellow River, and the Pei-ho 



I HAVE been much interested in the jjaper on the above rivers, 

 published in Nature, vol. xxii. p. 486. To the extent of the 

 writer's personal observations the calculations appear to have 

 been careful and accurate, and as near the truth as the observa- 

 vations of a single year are likely to be. A reference to Sir 

 Charles Hartley's observations of the Danube, extending over 

 ten years, shows that the mean maximum discharge of that river 

 for one year exceeded the minimum by 3 to I. 



It is however to the use of one observation of the Yellow River 

 made in 1792 by Sir Geo. Staunton that I feel compelled to 

 enter a protest, firstly, because one observation is misleading in 

 drawing general inferences, and, secondly, is especially to be 

 suspected when it is at variance with other well authenticated 

 examples. 



According to the writer of the paper, the mean discharge of 

 the Yang-tse is 770,397 cubic feet per second, carrying to the 

 sea 6,428,800,000 cubic feet of sediment per year, but the Yellow 

 River having only a mean discharge of 116,000 cubic feet per 

 second delivers, accordingto Sir George Staunton, 17,520,000,000 

 cubic feet of sediment per year into the Gulf of Pe-Chiii. With 

 Dominie Sampson we may well exclaim " prodigious ! " It has 

 struck me as an explanation of this anomaly that Sir George 

 Staunton probably measured the deposit from "the gallon and 

 three-quarters " of the Yellow River water as wet mud. 



If so this will at once account for the excessive amount of it. 

 The deposit of Nile mud in the reservoirs of the Cairo water- 

 works often amounts to I inch in 10 feet of water,' or ^^ part 

 of the bulk. Dr. Letheby's analyses show that in August the 

 proportion by weight of sediment (dried) being the maximum of 

 the year, in Nile water is J7u° : thus taking the specific gravity 

 of the dry mud at i '9, the measurement of the wet deposit by 

 bulk exceeds the dry about io\ times. 



If the 80 grains to the pint of the Yellow River water be 

 divided by loj, we arrive at between 7 and 8 grains per pint of 

 dry sediment, corresponding closely with the proportion given 

 by the writer for the Pei-ho and Yang-tse. 



I would also point out that the discharge of the River Plate 

 as given in the table is not the 7nean, which has not yet been 



■ "Mediterranean Deltas." Edin. Re-jiew, January, 1877. 

 = "Egyptian Irrigation." Second Report, January, 1S76. By John 

 Fowler, engineer to the Khedive. 



ascertained, but the dry veather Jhw^ Still another little error, 

 for which the writer is in no way responsible, being a quotation 

 from Huxley's " Physiography." The discharge of sediment by 

 the Thames is a calculation by Prof Geikie on an hypothesis, not 

 on observation; and instead of 1,865,000 should be 18,650,000 

 — this printer's error has been copied from Geikie's original 

 paper by writer after writer without discovery. 



I should feel obliged if the writer would explain why the 

 surface-current of the Yang-tse and Pei-ho should vary so in 

 velocity with the same average depth of water. It seems 

 anomalous. T. Mellard Reade 



Blundellsands, Liverpool 



Miller's Elements of Chemistry — Part III. Organic 

 Chemistry 



In his notice of the new edition of this work, by Mr. Groves 

 and myself, which appears in Nature, vol. xxii. p. 530, Mr. 

 Muir refers to an obvious omission at p. 933. May I request 

 those who possess the book to insert at the top of the page the 

 words " Probably, however, the most weighty objection that can 

 be raised to the "... Although in the revise, by some strange 

 mischance this line has been dropped in printing off 



Henry E. Armstrong 



Swiss Chalets 



Identical suggestions to those of Mr. George Henslow w ith 

 regard to the connection in descent of modern S" iss chalets with 

 ancient pile lake-dwellings will be found expressed in Dr. J. J. 

 Wild's "At Anchor" (Marcus Ward and Co.), p. 106, and with 

 some detail in my "Notts by a Naturalist on the Challenger" 

 (Macmiilan and Co.), p. 399. Dr. Wild, who is a native of 

 .Switzerland, and I arrived at the same conclusions independently, 

 as we only found out on reading one another's books, from the 

 study of the modern pile dwellings of the Malay Archipelago 

 during the voyage of the Challenger, and we both amongst other 

 conclusions identified the lalcony of the chalet with the ancient 

 platform, as does Mr. Henslow. H. N. MosELEY 



New University Club, St. James's Street, S.W. 



Spectre of the Brocken'at Home 

 Having occasion ten days ago to go into my garden about 

 half past ten o'clock at night 1 found there was a thick white 

 fog, through which, however, a star could be seen here and 

 there. I had an ordinary bediocm candlestick in my hand with 

 the candle lighted, in order to find the object I wanted. To my 

 great surprise I found that the lighted candle projected a fantastic 

 image of myself on the fog, the shadow being about twelve feet 

 high, and of an oddly distorted character, just as the spectre of 

 the Brockeu is said to be. It is of course usual on going into 

 the open air to use a lantern with a solid back for any light that 

 may be wanted, and with this, of course, such a shadow would 

 not be seen ; but in this charmingly foggy valley of the Thames, 

 and in these days of "Physics without Apparatus," the efiect I 

 saw can probably be seen only too often. May not the gigantic 

 spirits of the Ossianic heroes, whose form is composed of mist, 

 through which the stars can be seen, be derived from the fantastic 

 images thrown upon the mountain fogs from the camp fires of 

 the ancient Gaels ? In a land where mists abound a superstitious 

 people might very readily come to consider a mocking cloud- 

 spectre to be supernatural, though it was really their own image 

 magnified. If it be true that in our earlier stages of develop- 

 ment we resemble more nearly the past forms of life and thought, 

 I may mention in this connection that, thinking to amuse a little 

 child of three, I threw a magnified shadow of her on the wall 

 with a candle, and then, by moving it in the usual way, made the 

 figure suddenly small. Instead of ihe changing shadow giving 

 the pleasure intended, the child was terrified, as the warriors of 

 Morven may have been when they saw their shadows on the 

 clouds. J. INNBS Rogers 



Putney, October 8 



Ice under Pressure 

 There is a point in Dr. Carnelley's letter (Nature, vol. xxii. 

 p. 435) which I have been hoping to see cleared up by sub- 

 sequent letters. He says, " In order to coi.vert a solid mto a 

 ' R«port by James Cateman, C.Ii. 



