This distinguished gentleman died two years ago. He left by will his large, choice, and most valuable collection of engravings to Harvard College, together with a fund of sixteen thousand dollars to defray the expense of cataloguing and preserving them. But the most important of his legacies for public objects is that of fifty thousand dollars, as described in the extract from his will, quoted by William Gray, his nephew and executor, in a letter addressed to the corporation, dated Boston, Dec. 20, 1858, as follows:

"And also give, out of such surplus only, to Harvard College, or such other institution as you see fit, the further sum of fifty thousand dollars; the income to be applied to establishing and maintaining a Museum of Comparative Zoology; not to be appended to any other department, but to be under the charge of an independent Faculty, responsible only to the Corporation and Overseers. No part of said income is to be expended for real estate or the payment of salaries."

The conditions under which this donation has been bestowed on Harvard University are as follows:

"First, That the same be kept as a separate and distinct fund, and invested from time to time at the discretion of the Corporation, provided that no part thereof shall ever be invested in real estate, or in the shares or stock of any incorporated or joint-stock company.

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Second, No part of the income of said fund shall ever be expended for real estate or the payment of salaries.

"Third, The income is not to be subject to any charges of any nature, but the whole amount derived from the fund is to be applied to establishing and maintaining a Museum of Comparative Zoology at Harvard College.

"Fourth, Neither the collections, nor any building which may contain the same, shall ever be designated by any other name than the Museum of Comparative Zoology at Harvard College.

"Fifth, The Museum shall never be appended to any other department, but is to be under the charge of an independent Faculty, responsible only to the Corporation and Overseers.

"Sixth, The President of the College shall be the President of the Faculty, which shall be composed of four members besides the President. In case of vacancies in their number, other than that of President, the Faculty shall from time to time nominate to the Corporation persons to fill such vacancies; and if confirmed by the Corporation, such persons are to become members of the Faculty; if rejected, new nominations shall be made by the Faculty to the Corporation.

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Seventh, The Faculty are not to be at liberty to expend any part of the income of the fund, unless previously placed at their disposal by the Corporation.

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Eighth, The first Faculty shall consist of Rev. Dr. James Walker, President of the College, Professor Louis Agassiz, Director of the Museum, Dr. Jacob Bigelow, Professor Oliver Wendell Holmes, and Professor Jeffries Wyman.

"Ninth, In case of the loss of any part of the fund, so much of the income as may be requisite for this purpose shall be retained to make good such loss, provided that not more than one-half of the income shall be so retained in any one year.

"Tenth, That the Corporation enter this donation, with its conditions, upon their records, and vote to accept the same."

The conditions above prescribed are most judicious. The object for which the fund is established, in their nature cannot change. But there still remained other objects which imperatively demanded to be provided for. The collections of Professor Agassiz are at present in a small wooden building, which the torch of an incendiary might in an hour reduce to ashes, and thus annihilate the fruit of twelve years toil. Attention has been repeatedly called to this subject, and the announcement that Mr. William Gray, in the exercise of the discretion vested in him by his uncle's will, had decided to give the fifty thousand dollars for the support of the Museum, with the limitations already recited, seemed to be a sufficient reason for bringing the necessity of a fire-proof building again. before the public. The matter was forcibly presented by Prof. Agassiz to the Visiting Committee of the Scientific School, in January. We give an extract from this document, which has been printed by order of the Overseers.

"I have laid out a plan which I will simply submit to you. I am afraid you will consider it extravagant, but if I understand rightly the aspirations of the young men with whom I am every day brought into contact, I cannot consider it over-sanguine, or doubt that the time is coming before long, when the scientific progress of the country will demand such an institution.

"My hope is that there shall arise upon the grounds of Harvard a Museum of Natural History, which shall compete with the British Museum and with the Jardin des Plantes. Do not say it cannot be done, for you cannot suppose that what exists in England and France cannot be reached in America. I hope even that we shall found a museum which will be based upon a more suitable foundation and better qualified to advance the highest interests of science than these institutions of the old world.

"But although I have sketched a plan for such a museum, I am nevertheless fully aware that, at the beginning, it must be carried out in a manner commensurate with the probable means that may be secured. Let us first erect a wing of that ideal museum, at an expense of perhaps $50,000, or, if that is too much, let us limit ourselves to such rooms as will give fitting shelter to the collections already on hand, and secure them from the danger of fire and other casualties. A spark of fire in this slight wooden building, where the collections are now heaped together, would be sufficient to destroy in half an hour the collections which it has cost me twelve years to amass, and which I can truly say is the most valuable collection for the student of natural history on this continent, and, in some of its classes, superior to any in the world. The mere possibility of unpacking what is already in our possession under this roof, crowded together in barrels and boxes, inaccessible to myself or the students, of displaying them to the public, and making them useful for study, will, I have not the slightest doubt, be a sufficient stimulus in the community to secure what will be needed to finish the structure and to render it worthy of the institution with which it will be connected, and the enlightened people who understand that in our age, culture is the

only true distinction among nations. One thing only should not be overlooked, that whenever any structure is put up for the museum, it should not be built in a corner where it cannot grow, but be placed on such grounds as will never be an impediment to its indefinite increase.

"In its present condition the museum hardly furnishes me the specimens I require for my courses of instruction, for, in consequence of the daily accessions which are heaped upon those already crowded in this narrow space, it is often impossible to find what is wanted at the time, and it is out of the question to allow free access to the Museum in its present confused state, to any student not already trained in the manipulation of specimens. Had I six or eight rooms of the size of the two now at my disposition, I could at least make a fair beginning of a systematic arrangement, separate the duplicates from what is to constitute the collection proper, allow free access to the rooms for the public as well as the students, and thus create a more general interest for this establishment, while the students themselves would derive all the advantages which such a collection ought to afford them in their studies. At the same time, the separation of the duplicates from the collection proper would furnish ample materials for an extensive system of exchanges with other institutions of the same kind, by which the collection would at once be at least doubled in all its parts, and in some of its departments increased three or four times, and in some, even tenfold. The advantages of such a system of exchanges are very obvious, and my inability from want of room to separate the duplicates from the collection, has already been, for some years past, a check upon its increase. I hope, therefore, that as soon as it is fully understood, some remedy for this evil may be found.

"But even the possession of an appropriate building will not altogether put an end to our difficulties. The collection is already so large that it is impossible for me to take charge of it alone, even were I to give all my time to its care. For many years past I have already been under the necessity of having one or two, and at times even three assistants, who, at my private expense, have been, most of the time, engaged in taking care of the specimens. As I have nothing in the world but what I earn daily, such an expenditure has frequently been for me a source of unendurable anxiety, of which I wish to free myself, that I may hereafter devote whatever energy I may possess untrammeled to the higher interests of science. In this perplexity I have thought that a number of curatorships, (corresponding to the scholarships now existing in the university, which enable young men, whose private means are insufficient for such an object, to receive a college education) might perhaps be founded by some of our wealthy citizens, which would furnish a small income to students who have already taken their degree, and who, wishing to prosecute further their studies under my direction, might thus earn the means of remaining in Cambridge by assisting in the arrangement and preservation of the collection, as well as in making the exchanges. The position of the curators in the scientific school would thus be similar to that of the tutors in the undergraduate department. In a well organized museum there should be as many curators as there are branches in zoology, including embryology, paleontology and zoological anthropology. In the

course of time, the curatorships (to which should be attached the duty of delivering a certain number of lectures annually) may be endowed so as to afford the means of appointing special professors for each branch, and as soon as this is accomplished, our organization would be more perfect than that of either the British Museum or the Jardin des Plantes. Beside the curators, there should be one or two preparators, to mount specimens, and to make the necessary preparations required for the illustration of the specimens. It would also be desirable to have an artist attached to the establishment, who would have to make magnified drawings of such specimens as are too small to be at once studied by the natural powers of the eye; these drawings would be appropriate ornaments for the corridors, and at the same time assist in the courses of lectures which it should be the duty of every curator to deliver annually upon the special branches intrusted to his care."

The very able chairman of the committee, the Hon. John H. Clifford, made an earnest report, urging upon the Overseers and the community the importance of acting at once upon the suggestions of Prof. Agassiz. The interest which these communications immediately excited, was great and general, and steps were taken to carry out, or at least to commence the execution of the plan. Several meetings of the most distinguished and enlightened citizens of Boston have been held, and liberal sums have already been promised. A general subscription has been undertaken, with the certainty of success. Not only this, but the subject has already been brought before the Legislature, and there is strong ground to believe that a handsome appropriation will be made, from the moneys received by the State from the sale of the "Back Bay" lands. Governor Banks, in his annual message, called attention, in general but emphatic terms, to the value of the natural sciences, and has since shown a liberal disposition to favor this particular measure. The Hon. Charles Hale, Speaker of the House of Representatives-and one of the most rising young men in Massachusetts-is also understood to be a warm friend of the proposal. Other leading persons in the government look upon it with favor, and there seems little doubt that a majority of the Legislature will take the same enlightened view.

F.

4. Observations on the Genus Unio, together with descriptions of new species, their soft parts, and embryonic forms, in the family Unionidæ. 96 pages 4to, with 29 plates; by ISAAC LEA, LL.D. (From the Journal of the Academy Nat. Sci. Philad., 1858).-These researches constitute a volume, of which the first paper was read in Dec. 1857, and the remaining two in November, 1858. The embryonic form of the shell in the case of 38 species of Unionidæ is figured without details on one of the plates. The prevalent form is pouch-shaped, the height much greater than the length. In the last paper on new Unionide of the United States, numerous species are described and well figured. Dr. Lea observes that he has found the Unio cylindricus Say, U. rubiginosus Lea, and Anodonta imbecilis Say, sensitive to light, as if possessing some kind of visual organs, and that Prof. Haldeman had observed and published the same for the Unio radiatus. Mr. Lea's first publication on this point was in the Proceedings Acad. Nat. Sci. Philadelphia for February, 1857.

5. On the Stratification of Vesicular Ice by Pressure; by Prof. WILLIAM THOMSON, F.R.S., in a letter to Prof. STOKES, Sec. R.S., (Proc. Roy. Soc. from Phil. Mag., Dec. 1858.)-In my last letter to you I pointed out that my brother's theory of the effect of pressure in lowering the freezing point of water, affords a perfect explanation of various remarkable phenomena involving the internal melting of ice, described by Prof. Tyndall in the number of the "Proceedings" which has just been published. I wish now to show that the stratification of vesicular ice by pressure observed on a large scale in glaciers, and the lamination of clear ice described by Dr. Tyndall as produced in hand specimens by a Brahmah's press, are also demonstrable as conclusions from the same theory.

Conceive a continuous mass of ice, with vesicles containing either air or water distributed through it; and let this mass be pressed together by opposing forces on two opposite sides of it. The vesicles will gradually become arranged in strata perpendicular to the lines of pressure, because of the melting of ice in the localities of greatest pressure and the regulation of the water in the localities of least pressure, in the neighborhood of groups of these cavities. For, any two vesicles nearly in the direction of the condensation will afford to the ice between them a relief from pressure, and will occasion an aggravated pressure in the ice round each of them in the places farthest out from the line joining their centres; while the pressure in the ice on the far sides of the two vesicles will be somewhat diminished from what it would be were their cavities filled up with the solid, although not nearly as much diminished as it is in the ice between the two. Hence, as demonstrated by my brother's theory and my own experiment, the melting temperature of the ice round each vesicle will be highest on its side nearest to the other vesicle, and lowest in the localities on the whole farthest from the line joining the centres. Therefore, ice will melt from these last-mentioned localities, and, if each vesicle have water in it, the partition between the two will thicken by freezing on each side of it. Any two vesicles, on the other hand, which are nearly in a line perpendicular to the direction of pressure will agree in leaving an aggravated pressure to be borne by the solid between them, and will each direct away some of the pressure from the portions of the solid next itself on the two sides farthest from the plane through the centres, perpendicular to the line of pressure. This will give rise to an increase of pressure on the whole in the solid all round the two cavities, and nearly in the plane perpendicular to the pressure, although nowhere else so much as in the part between them. Hence these two vesicles will gradually extend towards one another by the melting of the intervening ice, and each will become flattened in towards the plane through the centres perpendicular to the direction of pressure, by the freezing of water on the parts of the bounding surface farthest from this plane. It may be similarly shown that two vesicles in a line oblique to that of condensation will give rise to such variations of pressure in the solid in their neighborhood, as to make them, by melting and freezing, to extend, each obliquely towards the other and from the parts of its boundary most remote from a plane midway between them, perpendicular to the direction of pressure.