Page:Science vol. 5.djvu/79

LETTERS TO THE EDITOR.

The muskrat carnivorous.

I HAVE seldom been more surprised than at the statement that the carnivorous habits of the muskrat have but just been discovered by scientific men. They are so often mentioned in treatises on American conchology, that a little reading would have prevented the error. Thus Dr. James Lewis says of the Unionidae, "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 Rodentia. 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 he 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 door of my boat-house is covered with shells, left by muskrats, every spring; and I have often stopped al the heaps of shells by their boles 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 le almost impossible to get the finest ones alive. The shells are large, but almost like paper; and the muskrat 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 beaver 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 carious circumstance. Very few of their shells are to be found on one shore of Onondaga Lake, which is fat 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 Benedictil 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 bold 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 mentioned 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 numerour cases where such hallucinations have coincided with the death for 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 Borde 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 persons 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 produce 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 hallucinations 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 affected 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 census as ours there are reasons why, quite apart from untruth, no 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 instinct 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 nos will to the end be quite double what It ought to be: In other words. the telepathic argument, if it prevails, will prevail, though based on data distinctly unfavorable to it.

As Professor Newcomb semedto confine his objection to the results of the census. I need not occupy your space with a description of the various precautions by which we ascertain that our cases of coincident visions-of verdical hallucinations-are bona fide records. Suffice it to say, that, whatever the possible 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 so amount that will not affect the validity of our general conclusions.

EDMUND GURNEY,

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

14 Dean's Yard, Westminster, S. 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, massive 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. sarvey, Washington, D.C.

Lake Mintassini

Your contributor, Prof. J. D. Whitney (Science, No. 100), is quite mistaken in ascribing the recent newspaper paragraphs referring to Lake Mistassini