was simply due to the persistent use of pine plank in walling the wells. Stone having to be brought from a distance, the early inhabitants have naturally taken the most available timber; and since the drift in which the wells are sunk is a tight clay, the decay of the sap and pitch of the wood has been confined to the water, instead of being carried away by easy drainage and gravelly subsoils.

This by no means exhausts the number of states in which surveys of one kind or another-principally geological-are in operation. Alabama, Georgia, Mississippi, North Carolina, and Tennessee, in the south; Indiana, Michigan, Missouri, New Jersey, Wisconsin, Rhode Island, and perhaps Kansas, in the north-all have persons employed with a larger or smaller force, with or without pay, making regular or occasional reports to legislatures or boards of agriculture. Probably the number could be increased. And surveys on a somewhat extensive scale have just been completed in New Hampshire, Ohio, and Illinois. In most cases, however, these surveys now in progress have mainly a local interest; and I have not, therefore, attempted to obtain special information concerning them.

There have also been a few private explorations of some interest; although during the past year comparatively little has been done excepting by the Peabody Museum of Archæology at Harvard College. Under the auspices of this new institution, Dr. E. Palmer spent ten months in Southern Utah and Northern Arizona exploring the ancient mounds. These are not such as have been used for burial, but appear to be formed by the successive ruins of mud - houses; one house being built upon the levelled heap which the ruins of an earlier one furnished, and, in its turn, giving place to another, when the first has been levelled by atmospheric agencies. They are therefore mounds of residence, or ancient dwelling-sites; and a considerable variety of curious pottery has been found in them. Similar pottery was found by Dr. Palmer in some rock-caves in the same region; and both are probably to be referred to the old Pueblo race. Dr. Palmer also made zoological and botanical collections of considerable interest, coming as they do from regions seldom visited by naturalists, discovering a number of new plants and insects. He has recently gone, in the interests of

the museum, to Mexico, accompanied by Dr. Parry, who will devote himself to botany.

Mr. Paul Schumacher has been exploring the island of Santa Catalina, off the southern coast of California. He has made some interesting discoveries concerning the manufacture of large stone pots, which, until the arrival of Europeans, or before 1650, the Indians made from steatite. He has found them in all stages of manufacture, and has even discovered the place whence they obtained the steatite. He also explored their burial-places.

Mr. Henry Gillman has been engaged in the same work in the burial-mounds of Florida, but no returns have yet been received.

Dr. C. C. Abbott has continued his examinations of the drift gravel of New Jersey with most interesting results, bringing to light what is deemed conclusive evidence of the existence of man on this continent during the glacial epoch. In gravel acknowledged by Hunt, Pumpelly, and Shaler to be either of glacial or interglacial age, he has found a large number of stone objects, unquestionably fashioned by artificial means. The discovery of implements in so many places where their presence cannot be referred to mere accident leaves no doubt in the minds of those who have examined the evidence that the conclusion of Dr. Abbott is essentially correct.

Finally, the curator of the museum, Mr. F. W. Putnam, spent a portion of last summer exploring the mounds, stonegraves, and earthworks of Tennessee. He believes he has obtained conclusive proof that the localities so frequent in the West, surrounded by embankments of earth upon an extensive scale, were sites of villages, the embankments being purely protective. This is opposed to the views of Morgan, who maintains that the village houses were built upon the encircling mound, and opened into the common area, where vegetables were grown. As relics of the mound-builders, Mr. Putnam brought home a large collection of skeletons, pottery, stone implements, pipes, and various articles of shell and bone. Seven perforated pearls were also found, and four copper articles. Parties are still in the field extending these explorations.

I have to mention one more expedition, which, though it

has nothing to do with our own territory, possesses an interest peculiar to itself. I refer to the north - polar expedition organizing by Captain Howgate, of our army. His plan is to establish a colony of fifty men, under military discipline, including three commissioned officers, two surgeons, an astronomer, and two or more naturalists, upon some point north of the eighty-first degree of latitude, on or near the shore of Lady Franklin Bay; to provision this party for at least three years, sending them annual supplies and recruits, and thus to make the colony the base of expeditions towards the pole. This differs from preceding plans, in leaving the party with no means of return until their work is accomplished; the only use of the ship being in transporting the men and supplies. They are to burn their bridges behind them. The advance to the pole is to be made with dogsledges, and the men are to live like the Esquimaux.

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This plan would certainly merit our heartiest commendation, did it not overestimate the importance of one single point-reaching the north pole. "From the post so formed," says Captain Howgate, speaking of his proposed colony, no time will be spent in needless quest along the shore, either east or west." The colony will "have their work narrowed down to a common focus-the pathway due north.” This is certainly a fatal error. It is of little consequence to geographical or any other science whether the pole be ever reached, however much the stimulus of adventure towards the pole may be needed to tempt men to explore high latitudes. But the knowledge which may be accumulated through such a colony, by explorations in every direction, would be of incalculable value, and, under proper direction, might form an addition to our knowledge of geology and terrestrial physics such as could never be gained elsewhere. Nowhere else can we so readily study the phenomena of the glacial epoch, the influence of which still shapes our lives and modifies all our surroundings. In no other quarter of the globe, as Professor Loomis has pointed out, can we make observations on the phenomena of magnetism, of atmospheric electricity, of the currents and varying temperatures of the air and water, which would possess so much importance in solving meteorological and other problems; while as to geography proper, nothing whatever is known of that re

gion but the bare shore-line, and even that is fragmentary. So far, then, from its being true that "surveys there have already been completed," as Captain Howgate urges, there is no quarter of the globe where more work is demanded, or where the result could be turned to better account. And Captain Howgate's plan must be placed upon a broader basis, if the expedition would expect to compete in any way with those fitting out by other nations.

Captain Howgate's faith in the ultimate approval and support by Congress of his plan of exploration has led him to fit out a preliminary arctic expedition to prepare the way for the main party, which, it is hoped, will organize the present year, and reach the Greenland coast by the middle of August at latest. This preliminary party sailed from New London in the Florence, a schooner of fifty-six tons, on the 2d of August, and reached Cumberland Gulf on September 13. Advices from them at the end of September announce their intention of moving at once into winter-quarters at the head of the gulf, near latitude 67° N. The party consists of thirteen persons, including a meteorologist and photographer, Mr. O. T. Sherman; and a naturalist, Mr. L. Kumlein, sent out by the Smithsonian Institution. They are expected to bring together ten Esquimau families, with their dogs and sledges, and fur clothing sufficient to supply fifty persons for three years, with other stores in readiness for the main party next year. They will also make meteorological observations and collections in natural history. When, next year, they have turned over the colony's outfit to the new party, they expect to capture and bring home a cargo of bone and oil sufficient to defray a part, at least, of the expenses of the trip. Notwithstanding, then, the failure of Captain Howgate's plan before the last Congress, we have an American party, with scientific men attached, stationed this winter within the Arctic Circle.

MICROSCOPY.

By Professor HAMILTON L. SMITH,

HOBART COLLEGE, GENEVA, N. Y.

LIMITS OF VISION.

Reasoning on certain data more or less theoretical, mathematicians of the first order, notably Helmholtz, had concluded that the limit of vision had been reached; that the optician could practically aid us no further; that, in short, the limits of possibility had been arrived at, since light itself is too coarse to reveal objects smaller than those visible to our finest and most powerful lenses. The limit marked out was about the one-hundred-and-eighty-thousandth of an inch. Recently the Rev. Mr. Dallinger, in a note read before the Liverpool Microscopical Society, gave instances of a remarkable kind—the result of his personal investigation, directed specially to this point-which were proved, by a method of measurement employed specially for the purpose, to carry the power of our most delicately constructed lenses considerably further than the mathematician considered possible, revealing, indeed, smaller objects than those mathematically indicated; and Mr. Dallinger did not by any means believe that he had wholly exhausted the power of visibility by these experiments. In reference to the same subject Mr. W. Webb states, in the Monthly Microscopical Journal for October, that Mr. Crisp, of London, has in his possession a diamond engraving of the Lord's Prayer in which the letters are smaller than the two-hundred-and-ten-millionth part of a square inch, at which size over fifty-nine Bibles would be required to cover an inch. Mr. Webb criticises somewhat severely the paper of Mr. Rogers, of Cambridge, Mass., "On a Possible Explanation of the Method employed by Nobert in Ruling his Test Plates," and makes some very obscure statements, to the effect that the spurious lines are caused by polarization of the light! According to the results of the undulatory theory of light, the size of the fringes of diffrac