NATURE 



[May 7, 1903 



he was very eager to get the meat out of it, and that when 

 later in the day he succeeded, he showed no manner of 

 misgiving as to his legal right to its possession. 



Other of my correspondents misunderstand the purpose 

 of the experiment. They see in it a desire to belittle their 

 canine pets. This was 'very far from my thoughts. We 

 have innumerable anecdotes telling us what dogs can do. 

 I wish, partly 1 admit with a view to enabling us to sort 

 these stories, to obtain, as data, definite observations show- 

 ing what dogs will not do. Into most dog stories there 

 creeps the little touch of human nature which makes them 

 and ourselves akin. 



Mine is the point of view of an anatomist. .A dog has 

 a brain very different from that of man. Brain and mind are 

 the two sides. of, the same coin; or rather, brain is the coin, 

 mind its value. The dog's brain cannot make a man's 

 thoughts. How near can we come to picturing to our- 

 selves the nature of a dog's thoughts? Without commit- 

 ting ourselves to Flechsig's theory of the division of the 

 cortex of the brain into " projection areas " and "associa- 

 tion areas," we may on anatomical grounds assert that 

 the cortex of a dog's brain contains fewer association 

 elements than does that of a man. It is an apparatus for 

 transforming sensory impressions into actions, in a more 

 limited and exclusive degree. Probably we can best picture' 

 to ourselves the work that it does by supposing that the 

 wordless thoughts of animals are direct combinations of 

 sensory impressions ; whereas man has invented symbols 

 for his sensory impressions. He works the symbols into 

 thought. Xor do his symbols stand for material objects 

 alone. They also stand for inferences from observations. 

 But this is a subject which perhaps I ought not to touch 

 without having at my disposal more space than I can ask 

 you to give me in your Journal. i 



We must admit with Sir William Ramsay that dogs make : 

 use, in their mental operations, of sensory impressions and 

 not of inferences, although I dissent from his qualification 

 of their impressions of smell as " vague." It is my object 

 to ascertain, by means, if possible, of observations which 

 can be made under properly controlled conditions upon 

 numerous dogs of various breeds, the limits of their power 

 of substituting inferences for sensory impressions as 

 materials of thought. 



Perhaps I may be allowed to use a new nomenclature in 

 defining the position in which, as it appears to me, we 

 stand with regard, to the axioms of animal psychology at 

 the present time. An animal remembers. When it per- 

 forms an action a picture of the action is stored) 

 in memory. If the result of the action be satis- 

 factory, a picture of this result is stored in memory. 

 When in future the animal desires to obtain the result it 

 repeats the action. This we may call the product of 

 " reasoning in the first degree." Action depends upon in- 

 ference. We may accept it as an axiom that an animal 

 can draw an inference of this kind. It is not yet estab-j 

 lished, by experimental methods, that an animal can com-- 

 bine two inferences, or, as I venture to term it, " reason 

 in the second degree." My box-experiment was intended^ 

 to throw light upon this question. I shall be very grateful 

 for any further suggestions of possible experiments of the 

 same kind. Alex. Hill. 



Downing Lodge, May 2. 



Spherical Aberration of the Eye. 



With reference to the experiment described by Mr. E. 

 Edser (p. 559) as appearing to have " escaped observation," 

 perhaps I may be allowed to state that this phenomenon 

 was (to the best of my recollection) described by me before 

 the School Natural History Society when I was a boy at 

 Rugby, about 1873-1874. I could not explain it, and no 

 one at the meeting had any suggestion to make. 



I think I connected it in my mind with irradiation 

 phenomena, though I was baffled by the fact that the whole 

 line is bent. 



If the black horizontal lines drawn between different 

 advertisements on the outside of Nature be held five or 

 six inches from the eye, and the rounded end of a pen be 

 brought down close to the eye, the whole line will be seen 

 to curve upward to meet the pen, becoming also blacker and 

 more distinct. \V. L. 



NO. 1749, VOL. 681 



The phenomenon mentioned by W. L. must have 

 frequently been noticed ; while resembling that described 

 by me as a proof of the spherical aberration of the eye, it 

 is yet due to an essentially different cause. The black line, 

 when placed at a distance of five or six inches from the eye, 

 is within the shortest distance of distinct vision from the 

 latter. A point source of light, situated on the axis of the 

 eye, at a position closer to the eye than the " near point," 

 produces a relatively large spot of light on the retina. If 

 the pupil be now progressively covered from above, the 

 rays passing through the middle and upper part of the 

 pupil will be cut off, so that those passing through the lower 

 part of the pupil alone remain ; these cut the retina in a 

 comparatively restricted area below the point of intersection 

 by the axis of the eye, so that the image apoarently rises, at 

 the same time becoming more sharply defined. Under the 

 conditions mentioned, the same phenomenon would be 

 observed if the eye were entirely free from spherical aberra- 

 tion. For this reason I stated that the black band should 

 be placed " just beyond the shortest distance of distinct 

 vision from the eye ; . . . care must be taken to keep the 

 eye carefully focused on the edge of the black band, or an 

 exag-gerated displacement, due to relaxation of the accom- 

 modation of the eye, may result." It was merely as a 

 proof pf the spherical aberration of th« eye that I described 

 this experiment as having apparently escaped observation. 



April 12. " Edwin Edser. 



In connection vvit'h ' the' experiment on the spherical 

 aberration of the eye, described in your issue of April 16, 

 1 may relate a striking observation I made some years ago. 

 Regard with one eye any light or bright object on the 

 wall, turn the head away until the object is just covered 

 by the line of the nose ; then move the eye to its natural 

 position, and the object will reappear, supposing the nose 

 is not too prominent. Moving the eye several times to and 

 fro, the phenomenon will be easily observed. 



Leipzig, April 29. W. Betz. 



THE SOLAR AND METEOROLOGICAL CYCLE 

 OF THIRTY-FIVE YEARS. 



THE fact that the rainfall of many regions of the 

 earth's surface has, for the last decade or more, 

 been gradually diminishing has led many Inquiries 

 to be made concerning the possible periodicity of this 

 meteorological element, and during the last few months 

 more general attention has been drawn to this Interest- 

 ing question. The great Importance of this inquiry, 

 not only to agriculturists but to others, renders it desir- 

 able that all facts which may tend to elucidate the 

 subject should be thoroughly discussed. 



The object of the present article Is to bring together, 

 without entering Into too great detail, a few statistics 

 relating to the rainfall of different stations In various 

 parts of the earth to see whether there be grounds for 

 assuming a continuation of the present small supply, or 

 whether a greater abundance may be looked for with 

 special reference to the condition of the British Isles. 



A few Introductory remarks may here not be out of 

 place. Eduard Bruckner first discovered that wet 

 periods, great droughts, &c., occurred at Intervals of 

 about thirty-five years, and he published his Important 

 conclusions In a volume w-hlch was, and still Is, a 

 valuable contribution to meteorological science. To 

 take one element only, namely, rainfall, Briickner 

 showed that during the last century the mean epochs 

 of the w et years were 1815, 1846-50, and 1876-80, while 

 those for the dry years were 1831-35 and 1861-65. 



Since the publication of this volume, many workers 

 have studied rainfall and other records extending over 

 long periods of time. Thus, to take one Instance among 

 many that might be cited, Herr Hofrath Julius Hann, 

 the distinguished late director of the Vienna Meteor- 

 ological Institute, made a minute investigation of the 



