Richthofen holds that the loess is a subaërial accumulation, due to the drifting action of the winds; to transportation by riv ulets from the hills immediately adjacent to each loess basin; and to the mineral material left over the basin by the growing grasses and other plants. The material for wind transportation is gathered from the circumjacent or even from remote rocks which were decomposed or disintegrated by alternate changes in temperature or humidity. The plants that covered the great plains served to stop the wind-drifted particles, and thus kept the accumulation ever in progress. Observing certain local differences in the appearance of the deposits which he studied, he invented the distinctions of land-loess and lake-loess. The last named was designed to account for certain indications of stratification or lamellation not to be adequately explained by the wind theory. The present system of drainage he accounts for much as do most other geologists, the main difference consisting in the assumption of great changes of climate causing heavy rains which led to floods. The usual indication of changes of level are also noticed by him, but they seem to have led to novel interpretation. Von Richthofen states that he found no evidence of a fresh-water fauna in the formations he studied, but land forms of molluscous and other animals abounded. he is directly opposed by the earlier and original observations of Pumpelly who distinctly states that he found fresh-water This view was first advanced by him in 1870 in a memoir on the geology of the provinces of Honan and Shansi. * Vide Am. Jour. of Sci. and Arts, Vol. XIV, p. 490, series third. 8 Vide Smithsonian Contributions to Knowledge, No. 202, pp. 42-43. That this author at that writing was convinced of the fresh water origin of the Chinese loess is attested by the following language. He says: "That this deposit was formed in fresh water, is shown by the presence of the shells found in the terrace of the Te Hai. The uniform character of the loam in the different basins, and in all parts of the same basin, its great extent, and the fineness of the material of which it consists, are conditions which prove that it is not of a local origin, or derived from the detr tus of neighboring shores, but that it was brought into the lakes by one or more large rivers which must have drained an area of great extent. Now throughout the region in question, the only rivers are those of the Yang Ho and Sankang Ho basia. and independently of the fact that these streams drain a very small area, the valley systems of these were almost entirely occupied by the lakes." Op. cit., p. 42. On p. 43 he derives the following argument from physical geography: "Indeed. all the information we possess concerning this region, goes to show that it has been the basin of a great lake, which once extended from the northern bank of the Ye low river southward to the mountains crowned by the Great Wall." These words were penned eleven years before the work of Richthofen appeared. forms in the loess regions on the borders of Mongolia. The points, however, which are mainly relied on by the Baron, appear to be (1) the presence of root-marks occurring throughout the formation; (2) absence of fresh-water or other aquatic life-forms; and (3) absence of stratification. Both the second and third of these propositions are met by the repeated statements of numerous careful observers, who have found aquatic and semi-aquatic forms in many localities. The presence of the semi-aquatic forins alone-such as Succinea-which are indicative of a moist. station, effectually negatives the assumption of a "dry, elevated area swept by fierce winds." The first proposition has been met by the studies of Professor J. E. Todd, who has shown that from the law which evidently obtains, that root-marks vary in frequency inversely as their distance below the present surface, “unusual care is necessary to interpret observations correctly." The conclusion reached by that observer is, that when correctly interpreted the distribution of root-marks opposes the sub-aërial hypothesis. It will have been observed that the original statements and inferences of Pumpelly and those of Richthofen were distinct and opposed. The former recognized the agency of water alone as sufficient to explain the phenomena he studied, while the latter alled to the aid of the winds a lake-basin, which in turn necesstated his artificial distinctions of lake-loess and land-loess. That such a distinction is wholly inapplicable to American deposits unquestionably true loess-is patent, for the reasons that presents a perfect homogeneity of structure, entire absence of any such modification as is seen in dunes-such as are true wind structures—and does present at several localities a faintly stratiFed appearance. Besides, the climatic conditions required by this Theory of the Chinese loess, seem to have had no counterpart in imatic changes over the areas covered by our loess. The argument for the lacustrine origin of the American deposits as been in part anticipated in the foregoing. But there should added the facts that here the formation is confined to river 'Proc. A. A. A. S., 1878, Vol. XXVIII. "Richthofen's Theory of the Loess, in he light of the Deposits of the Missouri." Professor Todd here shows that the er limit of root-marks-about forty-five feet-is approximately parallel with the resent surface. A table accompanies giving the depth of penetration of roots in "e loess. Those of the scouring rush (Equisetum lævigatum Braun) reached a ⚫nt more than twenty-five feet beneath the surface. valleys, and the high lands immediately adjacent; that of t fineness of its material, its composition, its rounded or tri rated form, the fossils imbedded in it, and the unmistakable acti of water in assorting; that of general continental depression sy chronous with its formation; that of the vast quantity of the n terial and its deposition alike on hill and in valley. These s erally and together are fatal to the hypothesis of Von Richtl fen. It is nevertheless beyond question that the loess, after position, has been somewhat modified by the action of stro winds, but the evidences of such action are purely local. I great dust-storms of Western Iowa, extending far beyond central portions of the State, which occurred in the spring 1880, will long be remembered in the annals of Iowa. For da the air was filled with fine dust, coming from the south-west, locality of the greatest areas of loess and the prevailing quar of the winds. That much of this fine material was carried m further away I have no doubt. The main effect however, of su wind storms, would be the denudation of the windward, and deeper covering of the leeward bases and sides of hills. Fossils. The mollusks of the loess belong, with perhap single exception, to genera which now flourish in regions adjac to the formation. They are Limnæa, Physa, Planorbis, Segment Pomatiopsis, Valvata, Amnicola, Sphærium, Anodonta, am fresh-water forms, and Hyalina, Stenotrema, Helicodiscus, Com Strobila, Helicina, Patula, Mesodon, Vallonia, Macrocyclis, P Succinea, Vertigo, and Cionella, among the land forms. Uni 1At the present day the Missouri flows past the western boundary of Iow an average rate of five miles per hour (Pacific R. R. Rept., Vol. 1, p. 232). fall per mile of this remarkable river, from the three forks of the Missouri t Joseph, varies from 31.59 to .88 feet, with an average for the whole distanc 1.55 feet per mile. It annually discharges into the Mississippi about four lions of cubic feet of water, and at the western boundary of Iowa it is not great an estimate to assume an annual flow of two trillions of cubic feet of w equaling one-tenth the whole discharge of the Mississippi. (See Humph and Abbott's "Report on the Mississippi River," p. 49.) The amount of sedi now being contributed by the Missouri to the Gulf is remarkable. From speci taken at Council Bluffs at both low and high water, Professor Emery determine amount in one gallon of the former at fifty-two grains, and in an equal quanti the latter at 404 grains. That, under the conditions prevailing at the time o loess deposition, the amount of sediment was very largely in excess of these fig is a fact beyond question, the material being, without doubt, furnished by the g ing of glaciers. These considerations should have their full weight in determ the dynamics of the loess of the Missouri region. quoted by Drs. Hayden and Aughey from the loess of Nebraska. There are thus, of mollusks, eleven genera attributed to freshwater, against thirteen genera to land forms. The single exception to varieties now living, as above noted, is Helicina, the species meant, H. occulta Say, being now extinct. It may be properly considered the only species characteristic of the loess. From the loess of east Central Iowa, at Iowa City, the chela of a Cambarus is reported, under circumstances which leave no doubt that it is from true loess. Of higher animals there have been found, especially in the Southern States, remains of Mastodon, Megatherium, Mylodon, Megalonyx, Castor, and Fiber, among others. Their remains and the relation of the loess to the drift, which, when both are present, it always covers, places its epoch at the close of the glacial period. (To be continued.) -:0: ICHTHYOLOGICAL PAPERS BY GEORGE POWERS DUNBAR, WITH Ą SKETCH OF HIS LIFE. A BY JACOB L. WORTMAN. STUDY of the fishes of the Southern States is one replete with many points of interest for the naturalist, and had it not been for a series of misfortunes, the credit for the earliest research into tus field would probably be due to an American student now nknown. It is the object of the present article, to give some nformation relating to the life and labors of this meritorious aturalist, which are of especial interest, since he was one of the irst native-born Americans who made an extended study of the chthyology of this region. The absence during his time of any eriodical devoted to the natural sciences in this country, conbuted much to his disadvantage, and as a consequence the chnical descriptions were withheld in anticipation of an opporunity to publish. This unfortunate circumstance is one of the uses of his obscurity, and is in part answerable for the loss of is many excellent observations in this branch. George Powers Dunbar was born in Baltimore, February 11th, 812. Nothing of unusual interest was noticeable in his early hiidhood, except an innate love for a study of natural history, on This statement now needs some modification. Since it was in type, a species of Helicina has been sent me in considerable abundance, taken in the vicinity of Iowa ty. That they are H. occulta Say, is hardly to be doubted. The forms sent all ap roximate the variety described by Green as Helicina rubella. 1A. H. Pilsbury, in litt. account of which his parents were doubtful of his future succes in life. He entered St. Mary's College, Maryland, at an earl age, and graduated from it with high honors in his eighteent year. The unfavorable outlook that science then presented for livelihood, induced him to look elsewhere for means of suppor Civil engineering was the profession that he chose, and the or that he practiced until his death. Having completed his studi in this branch, he was engaged on a survey of the Baltimore an Ohio, and the Portsmouth and Roanoke railroads from 1829 1835, a station on the former line still bears his name. In th early part of 1835, he removed to New Orleans, where he w employed on the Nashville railroad under Major Ranney. H was appointed Engineer of Public Works of the State in 183 which office he held until 1842, when he was elected surveyor the second municipality. This last office he retained with the e ception of a few months till the time of his death, which occurr on December 29, 1850, at the mouth of the Coatzacoalcos rive Mexico. Although in feeble health, Mr. Dunbar had accepted position with a corps of engineers, to survey the route for the T hauntepec railroad, where his health gave way entirely, and died on shipboard while en route to his home in New Orleans. At the early age of nine, he began collecting and arranging systematic order entomological specimens. In the course of a f years his collections on this subject amounted to several thousan specimens, which he afterwards presented to Dr. Luzenburg, New Orleans. The collection was afterward destroyed for wa of proper care. He was likewise familiar with the Flora of t South, and contributed something on the "Flora of the Dism Swamp." Shortly after leaving college, he began a careful stu of the classification, structure and habits of the fishes of the Sout ern States, which he continued with great zeal up to the time his death. All the time that could be spared from his profession duties was given to the pursuit of his favorite study, and he h prepared nearly all the plates and texts for an extensive volur which he was intending soon to publish. The volume was to co tain descriptions of over one hundred fishes, and was to be pr fusely illustrated by drawings from life made by himself. Ε last observations on some of the fishes of the Mexican coast, ma a short time previous to his decease, are still in existence and we probably the last that he intended to make before publishing work. In connection with his sad and untimely death we a |