March 17, 1881J 



NA TURE 



459 



representation of it with Balmain's luminous painl. When dry 

 the drawing may be hung up in the lecture-hall and covered with 

 black tissue-paper until required. At the appointed time the 

 lights are lowered, the tissue-paper withdrawn, and magneshim 

 wire burnt in front of the painting. I had- last week the pleasure 

 of showing this to an audience of 500 persons, and from the 

 expressions cf curiosity and approval found it to be a very 

 taking experiment. Wm. Ackroyd 



Sowerby Bridge, March 10 



Squirrels Crossing Water 



Having read in Nature the two interesting comniunicalious 

 on Squirrels Cro;sing Water, I was so free as to cite them in my 

 paper Lumiy, requesting the readers to let me know « hether any 

 of them had seen instances of squirrels taking to water here in 

 Bohemia. Upon this I received from my friend Prof. A Tiraseh 

 of Litomysl the following : — 



" Vou seem to doubt of squirrels taking to water, and I hasten 

 to give you notice of what I myself witnessed when a boy. With 

 the help of other young fellows like myself I succeeded in driving 

 a squirrel down from an old a^h-tree that stood in our garden, 

 not far from the River Medhuje (Metan). The squirrel must 

 have come from the other side of the water, where there was a 

 wood, and must have crossed the river. Of this however I 

 cannot be sure, bat when driven down from the tree, and seeing 

 its way to landward cut off, the squirrel turned to the river, and 

 sprang in, I following it. Now it swam very cleverly, but 

 was overtaken by me in the middle of the water, and brought 

 back in triumph, of cour. e with my hands all bleeding from its 

 sharp teeth, which the animal used cleverly too." 



Prague, March 13 T. V. Sladek 



Tacitus on the Aurora 



There is a passage in the "Germania" of Tacitus (chapter 

 xlv.) which I do not think can have ever been examined by the 

 historians of natural science, or it w ould have creeted a con- 

 siderable stir amongst them. Side by side with a plain account 

 — probably the earliest written one — of an arctic twilight, there 

 lurks in it a description of the aurora borealis, which moreover 

 lends countenance to the still prevailing notion that the northern 

 lights are accompanied by sound. 



Speaking of the Suiones, a tribe on the northern borders of 

 Germany, the great writer says : — " Beyond them Is another sea, 

 calm even to stagnation, by which the circle of the earth is 

 believed to be surrounded and confined ; because the last gleam 

 of the setting sun lingers till he rises again, and so brightly that 

 it dims the stars. It is believed too that a sound is heard, that 

 the forms of gods and rays from a head are seen (persuasio 

 adjicit sonum audiri iusuper formas deorum et radios capitis 

 adspici). Up to that point [however] — and the report [I have 

 given] is true — everything is natural." 



As to the question of sounds being heard, the din of carts and 

 factories in our city, and the roar of trains in our suburbs make 

 an observation here for determining it impossible; while the 

 rarity of the phenomenon in England generally keeps spectators 

 from being on the watch. But I have heard an intelligent old 

 man who has often gazed on the bright streamers during the clear 

 still nights of Aberdeenshire declare that he has plainly observed 

 sharp switching sounds to proceed from them. It seems to me 

 probable, since electricity can change into sound and takes part 

 in producing the aiu-ora, that the spectacle is attended by 

 audible vibrations. M. L. Rouse 



Chislehurst, Kent 



ON THE PRACTICABILITY OF LIVING AT 

 GREAT ELEVATIONS ABOVE THE LEVEL 

 OF THE SEA » 



" T J P to this time most of the loftiest portions of the 

 ^ earth are totally une.xplored, and this arises princi- 

 pally from the fact that the mountaineer, in addition to 

 experiencing all of the troubles which occur to other 

 travellers, has to deal with some which are peculiar to his 

 work. I do not now refer to the 'distressing haemor- 



^ Extracts made, by permission of ihe author, fiom a lecture delivered 

 by Edward Whymper to the Society of Arts in the Thealre at South Ken- 

 sington, March 9, 18S1— "On Chimborazo and Cotopaxi." 



rhages,' 'alarming vomitings,' and 'painful excoriations' 

 which are said to afflict him. Hemorrhage and excoria- 

 tion are rather large words, and they are apt to be alarming 

 if they are not translated. But they do not seem so very 

 formidable if they are rendered ' bleeding at the nose ' 

 and ' loss of skin through sunburn ' ; and it may perhaps 

 tend still further to allay alarm if I say that I have never 

 known bleeding at the nose to occur upon a mountain 

 except to those who were subject to the complaint ; while 

 with regard to vomitings, although such unpleasant oc- 

 currences do happen, they have only been known when 

 persons have taken that which has disagreed with them. 



" There is, however, behind these, another trouble, which 

 cannot be dismissed so lightly. All travellers, without 

 exception, who have ever attained to great altitudes, have 

 spoken of having been affected by a mysterious complaint, 

 and this complaint is known to affect native races living 

 in high mountain regions, as well as casual travellers. 

 With us it is usually called mountain sickness. There 

 are many native names for it, and numerous conjectures 

 have been put forward as to its cause. Very commonly it 

 is supposed to be the work of evil spirits, or mysterious 

 'local influences' : but there is no doubt that it is simply 

 an effect which is the result of the diminution in the 

 atmospheric pressure which is experienced as one goes 

 upwaid. The reduction which takes place at great heights 

 is quite sufficient to account for disturbance of the human 

 system. At 20,000 feet pressure is less than half the 

 amount that it is at the level of the sea : that is to say, 

 whereas at the level of the sea atmospheric pressure is 

 generally capable of sustaining a column of mercury of 

 thirty inches, at 20,000 feet it will not sustain a column of 

 fifteen inches. ***** 



" From air-ptimp experiments, and from purely philo- 

 sophical considerations, it is obvious that the human 

 system must be liable to derangement if subjected to 

 sudden diminution of the atmospheric pressure to which 

 it has been accustomed. These disturbances have often 

 been so severe as to render mountain travellers incapable, 

 and their lives well-nigh unendurable ; and it is scarcely 

 to, be wondered at that they have endeavoured to escape 

 from the infliction by descending into lower regions. I 

 do not know a single instance of a traveller who, having 

 been attacked in this way, has deliberately, so to speak, 

 sat it out, and had a pitched battle v.ith the enemy. Nor 

 am I aware that any one has even suggested the bare 

 possibility of coming out victorious from such an en- 

 counter. Yet, upon doing so, depended the chance of 

 pushing explorations into the highest regions of the earth ; 

 and I long felt a keen desire to know whether my own 

 organisation, at least, could not accommodate itself to the 

 altered conditions. From considerations which would 

 occupy too long to enter into now, I gradually acquired 

 the conviction that patience and perseverance were the 

 principal requisites for success ; and the journey of which 

 I am now going to speak was undertaken with the view 

 of bringing this matter, amongst other things, to a definite 

 issue. In the course of it we camped out at very great 

 heights. Twenty-one nights were'.spent above 14,000 feet 

 above the level of the sea ; eight more above 15,000 feet; 

 thirteen more above 16,000 feet; six more above i7,ooofeet; 

 and one more at 19,450 feet. I shall not now anticipate 

 what you will presently hear, and I have made these 

 preliminary observations to render less frequent the inter- 

 ruption of the narrative, and for the purpose of explaining 

 allusions in it vhich might otherwise perhaps have been 

 only half-understood." 



After describing the route taken to Chimborazo, Mr. 

 Whymper proceeded to mention the first journey he made 

 to that mountain ; and said that whilst returning frotn it 

 to the town of Guaranda (8870 feet), whilst still about 

 13,000 feet above the sea, he was overcome by dizziness, 

 feverishness, and intense headache, and had to be sup- 

 ported by two of his people for the greater part of ihe 



