5o6 



NATURE 



{Oct. 5, 1876 



which he was associated would have occurred in the valley- 

 gravels of Scotland, Ireland, and the northern and midland 

 counties of England, just as in those of the south-east." Mr. 

 Geikie makes a similar statement in his preface : — " A wide land- 

 surface existed in the British area after the disappearance of the 

 ice-sheet snd before the period of great submergence ;" and he 

 cites the discovery of the human fibula under glacial clay in the 

 Victoria Cave in confirmation. 



h It has always seemed to me that in discarding the power of 

 the ice-sheet for that of the "great submergence" as an agent for 

 the removal of all traces of an earlier fauna, Mr. Geikie, when 

 attacking the tree of prejudice, has cast down his axe and taken 

 up a whittle. Apart fiom the very doubtful extent and depth 

 of the submergence, its destructive powers cannot for complete- 

 ness be compared to that of the grinding of an ice-sheet In a 

 submergence, even if the beating of the surf destroyed all super- 

 ficial deposits — a supposition which.if applied, a coast so abound- 

 ing in land-locked and sheltered firths as Scotland partly sub- 

 merged would present, is in the highest degree improbable — the 

 rivers at least would carry down carcases into secure resting- 

 places and entomb them in estuary mud, and it would be most 

 unlikely that no such relics should be preserved when the land 

 rose again. But, on the other hand, it is difficult to believe that 

 any organic remains could escape the grinding of an ice-sheet 

 if continued through a long period. 



In ihe Victoria. Cave, at any rate, the surroundings are such that 

 nothing but an ice-sheet could have sealed up with glacial clay the 

 remains discovered by the Committee. The valley lies close by, but 

 is 9CX> feet deeper, and no advance of a mere valley glacier in the 

 supposed later increase of glacial conditions could have brought 

 the boulders to that height. The form and situation of the hill 

 near the top of which the cave lies is such, that no small ice- 

 field could have formed on it and brought this glacial dSbris. 

 The origin of the boulders, their position, the ice-scratches on 

 the rocks hard by, all point to the time of greatest glaciation 

 when the whole district probably was covered in with ice and 

 snow of great thickness. And the agent which closed the 

 cavern and concealed the animals within it must have been the 

 sime which swept the country clean ol their remains all around 

 further than the eye can reach. 



To sum up, the direct evidences as yet found to support, by 

 actual infraposition, the inter-glacial age of palaeolithic man and 

 of the fauna with which he is associated, are as follows : — 



I. Victoria Cave, Settle : — A human fibula under glacial till, 

 and associated with Elephas antiquus, Rhinoceros leptor/iinus. 

 Hyaena, Hippopotamus, &c. * 



2 At Wetzikon, Canton Zurich, a piece of lignite containing 

 basket-work lying beneath glacial deposits, and associated with 

 Elephas antiquus and Rhinoceros leptorhinus, ^ 



3. Near Brandon, Suffolk, i?nplements, with bones not yet 

 determined, in brick-earth beneath the great chalky boulder- 

 clay of East Anglia. 



There is nothing in any of these instances to support the 

 notion that this particular fauna lived subsequently to the age of 

 the Scottish ice-sheet and immediately prior to a great submer- 

 gence. 



The Settle till is undoubtedly of the age of the ice-sheet. 

 The Wetzikon lignite lies upon a glacial till beneath a river 

 gravel, and upon that are huge angular erratic blocks, " clearly 

 indicating the presence of a great glacier posterior in date to the 

 organic remains." *• 



The Brandon implements are beneath the chalky boulder clay 

 which Mr. Searles Wood, jun., believes to be the product of an 

 ice-sheet, though partly deposited beneath the sea, a condition 

 which is incompatible with the co-existence of a great submer- 

 gence. 



After, and in sole opposition to, such evidence, we can hardly 

 contentedly take the existence of frog and water-rat as upholding 

 the presence of paloeolithic man and his congeners in times later 

 than the great ice-sheet of Scotland. The Arctic mammals are, 

 of course, out of court and cannot be taken as evidence, for it is 

 highly probable that they returned with the retreat of the ice ; 

 but, so far, we have no evidence that this was the case with the 

 more tropical animals. 



My friend Mr, James Geikie will, I am sure, take these sug- 



' " The Relation of Man to the Ice-sheet in the North of England," 

 Nature, vol. ix., p. 14, 1873 ; also " Settle Caves Exploration," Brit. Assoc. 

 Keports for 1874 and 1875. 



' Rutimeyer; Archiv fiir Anthroiologie, 1875; also Natuke, vol. xiii. 

 p. 130. 



3 Lyell ; "Antiquity of Man," p. 368. "^ 



gestions in the friendly spirit in which they are offered. My 

 chief reason for bringing them forward is that we hear that a 

 new edition of his valuable work is in preparation, and it will 

 be a loss to geology if this matter be not foully discussed by one 

 who is so well able to hancile the subject in all its bearing«. 

 Meanwhile, we are deeply indebted to him for progress already 

 made, and also to my friend Mr. Skertchley for this important 

 addition to the evidence and the perspicuous manner in which 

 he has brought it before us, R. H. Tiddeman 



The Flame of Chloride of Sodium in a Common Coal 

 Fire 



Some time ago a correspondent of Nature (vol. xiii. p. 287) 

 inquired for an explanation of the fact that while common salt 

 (chloride of sodium) colours the flame of an ordinary spirit-lamp 

 yellow, the same substance thrown upon a common coal fiie 

 gives rise to a blue flame. In the next number (p. 306) Dr. 

 Schuster stated that the origin of the blue flame was still involved 

 in mystery, and (if my memory is correct, for I have not the 

 number at hand) that he and Prof. Schorlemmer had been en- 

 gaged in an investigation of the same. 



Dr. Schuster's letter shows that the question is not an unim- 

 portant one ; and as I have lately made a few experiments 

 which seem to confirm an explanation which occurred to me at 

 the time, I send a short description of them. 



The theory I put forward is that the blue flame noticed when 

 salt is thrown upon a coal fire (of bituminous coal) is possibly 

 due to the presence o{ carbonic oxide (CO), produced by a series 

 of reactions, through which the common salt is converted into, 

 first, sulphate, and then sulphide of sodium, as in the manufac- 

 ture of crude carbonate of sodium {black ash), all the reactions J 

 being simply carried out in one furnace instead of two. I 



Leblanc's process consists in — i. Converting common salt into 

 sulphate of sodium. 2. The "saU cake" is then mixed with 

 coal and limestone, placed in a furnace and heated strongly, 

 during which process a blue flame of carbonic oxide is observed to 

 play upon the surface. 



Now in the case we have under consideration, the only differ- 

 ence is that the salt is first converted into sulphate by the oxi- 

 dation of the iron pyrites, from which no coal is free (and, in 

 fact, it has been proposed to use such a process commercially, 

 viz. , by roasting common salt with iron pyrites). 



At this stage, then, the reaction going on in the fire will be 

 expressed by the equation — 



4NaCl + 2FeS + Ojj = 2NaaS04 -f Fe^Og + CI4. 



Almost simultaneously with this, the carbon of the coal comes 

 into play, reducing the sulphate of sodium to sulphide, thus — 

 Na2S04 -t- C4 = Na-,S -f 4CO (carbonic oxide). 



Of course were any substance present answering to the lime- 

 stone used in practice, as may occur in the ash, we should have 

 the full conversion to " black ash," viz. : — 

 eNajS -1- SCaCOj -f Cg = eNa^COa + 6CaS + 2CaO -f 4CO, 

 with a further evolution of carbonic oxide. 



I need not say that carbonic oxide burns with a violet blue 

 flame perfectly indistinguishable from that produced by throwing 

 salt into a bituminous coal fire. This may be proved at once by 

 experimenting with a fire of anthracite, which itself only gives 

 the slight lambent blue flame of carbonic oxide. The presence 

 of salt makes no difference whatever in the colour of this flame, 

 and it is difficult indeed to determine whether the salt is ignited 

 at all. The difference in the two cases is just this : — A common 

 coal fire has usually a large, bright, or smoky flame. Salt 

 thrown on it diminishes its size and brightness by robbing it ot 

 free carbon or hydrocarbon — which gave it those qualities, and 

 which is derived from the volatile matter — as in the reactions 

 above set forth, the result being the production of carbonic oxide. 

 In the case of anthracite, however, the free carbon is absent ; 

 but the carbonic oxide exists, and is equally apparent before and 

 after the addition of salt. It is possible that the heat, instead of 

 volatilising the sodium compounds and so giving the yellow 

 flame, is expended in effecting the new chemical transformations. 



In the case of a spirit-lamp or of a Bunsen burner there is no 

 supply of carbon, nor is there any iron pyritts to be converted 

 into sulphuric acid, consequently the above complicated process 

 cannot take place, and the flame only shows the sodium colora- 

 tion. 



The following laboratory experiments were made with a view 

 to test the accuracy of these speculations : — 



