January 23, 1885.] 



SCIENCE, 



65 



LETTERS TO THE EDITOR. 

 The muskrat carnivorous. 



I have seldom been more surprised than at the state- 

 ment that the carnivorous habits of the muskrat have 

 but just been discovered by scientific men. They 

 are so often mentioned in treatises on American con- 

 chology, that a little reading would have prevented 

 the error. Thus Dr. James Lewis says of the Uni- 

 onidae, " They afford abundant food for the muskrat 

 and mink;" and like quotations might be given. 

 But the fact is not left out of sight in treatises on 

 the Kodentia. In the * Mammalia of New York,' 

 published by the state, De Kay says of the muskrat, 

 " It is also extremely fond of the fresh-water mussel 

 (Unio), heaps of which, in a gnawed or comminuted 

 state, may be found near their retreats." Tenney's 

 'Zoology,' a mere schoolbook, says, "Muskrats feed 

 upon mussels, and roots of grasses, and aquatic 

 plants." To my knowledge, they feed on Unios 

 throughout the year, but mostly in winter and spring. 

 The floor of my boat-house is covered with shells, left 

 by muskrats, every spring ; and I have often stopped 

 at the heaps of shells by their holes to see what 

 species occurred near. The fact that they eat fish 

 has certainly been less known. - 



There seem to be four principal ways in which 

 muskrats get at the animal in the mussel-shell. In 

 a small lake near me there are very fine specimens 

 of Anodonta fragilis, but in such situations that it 

 is almost impossible to get the finest ones alive. The 

 shells are large, but almost like paper; and the musk- 

 rat invariably tears off one valve. In the thicker 

 shells of Seneca River, not far off, its common way is 

 to break the thinner end of the shell. In the much 

 heavier shells of the west and south, I have heard 

 that they either gnaw the hinge-ligament, or allow 

 the animal to freeze and open. 



"While speaking of the Unionidae, I may mention a 

 curious circumstance. Yery few of their shells are 

 to be found on one shore of Onondaga Lake, which 

 is flat and marly; and this is partly so because the 

 animal burrows deeply in the tenacious mud, and is 

 not easily dislodged. But I passed that shore one 

 day when a number of Anodonta Benedictii were 

 washed in. They were helpless in the waves; but, 

 when they had rested a while on the beach, they got 

 up on edge, protruded the muscular foot, got a firm 

 hold on the marl, and worked their way back to the 

 water with apparent ease. W. M. Beauchamp. 



A census of hallucinations. 



In a letter which you published on Dec. 5, I men- 

 tioned a sort of census whereby we are inquiring 

 what proportion of the population has experienced 

 waking visions of absent friends; the object being to 

 discover how far chance may account for the numer- 

 ous cases where such hallucinations have coincided 

 with the death (or some serious crisis in the life) 

 of the person whose presence was suggested, or how 

 far, on the other hand, these cases drive us to some 

 such hypothesis as ' telepathy.' In a letter published 

 by you on the same day, Professor Newcomb has 

 objected that untrue answers may be given by per- 

 sons wishing to amuse themselves at our expense. I 

 am far from denying that persons may exist who 

 would be glad to thwart us, and amuse themselves, 

 even at the cost of untruth. But when the question 

 is put, "Do you remember having ever distinctly 

 seen the face or form of a person known to you, when 

 that person was not really there?" it is not at once 

 obvious whether the amusing untruth would be ' yes ' 



or 'no.' In neither case would the joke seem to be 

 of a very exhilarating quality; but, on the whole, I 

 should say that 'yes' would be the favorite, as at 

 any rate representing the rarer and less commonplace 

 experience. ' Yes ' is, moreover, the answer, which, 

 as a matter of fact, it has been very generally thought 

 we ourselves preferred; so that to give it might pro- 

 duce a piquant sense of fooling us to the top of our 

 bent. But a moment's reflection will show, that, so 

 far as the census might be thus affected, it would 

 be affected in a direction adverse to the telepathic 

 argument; for the commoner the purely casual hal- 

 lucinations are reckoned to be, the stronger is the 

 argument that the visions which correspond with 

 real events do so by chance. And if the number of 

 these coincident visions makes the chance-argument 

 untenable, even when the basis of estimation is af- 

 fected in the way supposed, a fortiori would this be 

 the case if the yeses were reduced to their true 

 number. 



While on this point, I may add that in such a cen- 

 sus as ours there are reasons why, quite apart from 

 untruth, an unfair number of yeses are sure to be 

 obtained. One chief reason is, that, when forms 

 to be filled up are distributed on a large scale, it is 

 impossible to bring it home to the minds of many 

 of the persons whose answer would, be 'no,' that 

 there is any use in recording that answer. Their in- 

 stinct is, that results, to be of scientific value, must 

 be positive, like natural-history specimens. This 

 difficulty has been encountered again and again; and 

 I feel little doubt that the proportion of yeses to noes 

 will in the end be quite double what it ought to be : 

 in other words, the telepathic argument, if it pre- 

 vails, will prevail, though based on data distinctly 

 unfavorable to it. 



As Professor Newcomb seemed to confine his objec- 

 tion to the results of the census, I need not occupy 

 your space with a description of the various precau- 

 tions by which we ascertain that our cases of coin- 

 cident visions — of veridical hallucinations — are bona 

 fide records. Suffice it to say, that, whatever the pos- 

 sible sources of error in our evidence may be, — and 

 there are some which demand unceasing care and 

 watchfulness, — deliberate hoaxing is a danger which 

 we believe we can reduce to an amount that will not 

 affect the validity of our general conclusions. 

 Edmund Gurnet, 

 Hon. sec. of Soc. for psych, research. 



14 Dean's Yard, Westminster, 8. W., 

 Dec. 22. 



Dikes of peridotite cutting the carboniferous 

 rocks of Kentucky. 



Prof. A. R. Crandall, of the Kentucky geological 

 survey, has recently discovered in Elliot county, of 

 that state, several dikes of very interesting peridotite, 

 which intersect the carboniferous formation. It very 

 rarely happens that such youthful felspar-free, mas- 

 sive rocks occur in regions of so little disturbance as 

 eastern Kentucky, and under such circumstances that 

 their eruptive character can be established beyond 

 question. Professor Crandall and myself, with the 

 approval of the U. S. geological survey, hope to be 

 able to give these rocks the careful study they ought 

 to receive. J. S. Diller. 



U. S. geol. survey, Washington, D.C. 



Lake Mistassini. 



Your contributor, Prof. J. D. Whitney (Science, 

 No. 100), is quite mistaken in ascribing the recent 

 newspaper paragraphs referring to Lake Mistassini 



