212 



NATURE 



[April 13, 191 r 



tlie sea-serpent : whether we refer what was uecn to long 

 lines of ducks now dropping out of sight in the trough of 

 the wave, now rising in thick coil over its crest; or to 

 water-logged baulks of timber with seaweed hanging like 

 a mane about the ends, which were protruded or sub- 

 merged with the rise and fall of the waves ; or whether 

 wc accept Giinther's explanation of the best authenticated 

 ( asc on record, which he described as a sperm whale 

 attacked by an octopus, the dimensions of which he calcu- 

 lated from known examples ; we admit the stories and 

 discuss only the explanations, which in these last cited 

 cases must differ so much. 



So for Mr. Day's story of the fox and the fleas; we 

 may examine it from several points of view. If it is a 

 true natural history story it is extremely improbable that 

 Mr. Day's was the first and only recorded fox who showed 

 this instinct, or, as Samuel Butler would call it, 

 "memory"; and, thanks to many friends, I can give 

 more or less clear references to previous observations of 

 the same kind. Mr. Nichols tells me that he has heard 

 it mentioned as a story current among Celtic people — 

 likely enough, as they are chiefly pastoral and close 

 observers of natural phenomena. Mr. Grey in his letter, 

 which by your courtesy I have seen, thinks he remembers 

 it as belonging to Gascony. But the most important con- 

 tribution to the discussion, so far, is a reference sent by 

 my friend and pupil Mr. Frank Barclay, 

 which I have verified in the university 

 library. 



Olaus Magnus, writing in 1555, 

 says : — 



" Praeterea ciim pulices habet, fasci- 

 ruliim mollis foeni ore accipit pilis 

 involutum, scque paulatim posterius 

 inchoando in aquam mergit, ac totum 

 corpus, ut pulices aquam fugientcs, ad 

 caput ascendant. Deinde caput im- 

 mergit, ut in foenum fugiant ; quo 

 facto, foenum relinquit in aqua, et 

 mox enatat. " 



Besides, when he has fleas he takes 

 in his mouth a bundle of soft hay rolled 

 up in hair, and gradually immerses 

 himself in the water back end first, and 

 then his whole body, so that the fleas, 

 trying to escape from the water, may 

 creep up to his head. Then he draws 

 his head under water that the fleas 

 may be driven to take refuge in the 

 hay, and when this has been done he 

 lets the hay go in the water, and forth- 

 with swims out. 



The amusing figure which Olaus 

 Magnus gives in illustration of the 

 various cunning devices of foxes which he describes has 

 been admirably reproduced by Mr. Edwin Wilson. 



Foenum pilis involutum is not quite clear. Mr. Day 

 does not remember anything about hay, and in Olaus 

 Magnus's picture there is nothing like hair or wool shown ; 

 but the word is late Latin, and may be used as loosely 

 as the modern " pile," which is either hair or the soft. 

 Huffy nap taken off the surface of cloth. That is, how- 

 ever, unimportant. But I was given an interesting fact 

 in corroboration of the probability that the fleas would 

 readily betake themselves to a^wI. Miss Parsons, of 

 Horseheath, a shrewd observer of natural phenomena and 

 collector of folklore, told me that it was a common opinion 

 among farm people that if poultry and poultry houses were 

 infested by fleas the best way to get rid of them was to 

 drive a flock of sheep among them, as every flea would 

 take to the wool. 



There is another point to be considered — I do not know 

 that a fox is an animal much troubled by fleas. It may 

 be that the curious procedure on the part of Mr. Day's 

 fox was not a thing of common occurrence, but only when 

 the animal had the misfortune to be suddenly attacked by 

 an abnormal number ; for great swarms of fleas do 

 suddenly appear, not only on certain individuals or groups 

 of animals, but on walls and wooden partitions. Some of 

 your readers will remember the story of Dr. Michael 

 Foster's dog and the fleas, which he carried in from a 

 wall outside the house. I have mvself seen the wooden 



frame of a hot-b«.'d covered with them, and bometim-^ . 

 hedgehog carries an enormous number. 



A fox s calling takes him occasionally to h*'n hou«'i&, 

 and commonly to earths frequented by hedgehogs, and he 

 might therefore sometimes have to lake strong measures i 



to g«'t rid of the excessive number of fleas he had carried 

 from such places. 



Mr. Day vouches for the truth of the story as I gave 

 it in your issue of March 23, except that the hurdles and 

 straw were put up to shelter him and his father, and no- 

 to protect sheep and lambs, for it was in July <i843). 



The fox went into a deep part of the small stream that 

 runs by Mob's Hall into the Rhee or Cam n<-ar Thistly- 

 ground F'arm, about a mile west of Guilden Morden. 



T. McKessy HucHts 



Ravensworth, Brooklands Avenue, Cambridge. 



The Radiation producingr Aurora Borealis. 

 As is well known. Prof. Birkeland has put forward the 

 hypothesis that aurora borealis and magnetic disturbances 

 are due to an " electric radiation " coming from the sun. 

 The numerous observations, partly from the n-gions near 

 the auroral zone, treated by Birkeland in his work " The 

 Norwegian .Aurora Polaris Expedition, 1902-1903," as 

 well as the theoretical work by Prof. Stormer, have shown 

 that this hypothesis in a verj* satisfactory way account- 



NO. 2163, VOL. 86] 



for the characteristic properties of aurora and magnetic 

 disturbances, as well as regards occurrence as with respect 

 to distribution in space relative to the earth. 



The phenomena of aurora and magnetic storms, how- 

 ever, show a great variety of forms, and further knowledge 

 will be required until we are able to follow every single 

 phenomenon into details. From the point of view of 

 Birkeland's hypothesis, it will be the next step to deter- 

 mine more definitely the properties of those " electric 

 rays " which in the various cases produce the aurora and 

 magnetic storms. 



From the position of the auroral zone, Birkeland has 

 already (Compfes rendus, 1910) estimated the average stiff- 

 ness of the rays as measured by their deviation in a 

 magnetic field, and he found that the rays are ten times as 

 stiff as ordinary a rays. 



The question would now naturally suggest itself. Is the 

 " electric radiation " of the type of /3 rays consisting of 

 corpuscles or of the type of o rays consisting of atoms? 

 It is my intention in this note to direct attention to certain 

 points which may guide us regarding this question. 



-As is well known, the law governing the absorption of 

 the rays by matter is very different for the two types. 

 The o rays penetrate matter in nearly straight-lined orbits, 

 and only a very small fraction is scattered to any appreci- 

 able amount. The velocity of the o particle gradually 

 diminishes as the particle passes through matter, and for 

 a certain velocity it loses its power of ionising the mole- 



