as much by causing ships to go fewer miles as by causing them to go faster. This generation is familiar with the part that has been played by steam propulsion in increasing the speed of ships, but, besides the increase in the rate of travel, modern motive power, by making possible a departure from the old meteorological routes, has had another and a greater effect in the progress of the universal policy of civilized nations to accelerate transit from place to place to the utmost possible extent. When the wind was the sole motor of ocean-going vessels the best economy was realized by passing through regions of favorable meteorological conditions without reference to the directness of the route. Thus, in sailing from Europe to the United States, it was customary to pass southward along the eastern shores of the Atlantic to the Cape Verde Islands, and thence westward through the trade-wind region along the route followed by Columbus on his first voyage to the New World, and finally northward into the region of prevailing westerly winds and along the western the western shores of the Atlantic to the point of destination. In making this voyage, ships traversed 4,400 miles in passing between ports that were only 2,400 miles apart on the surface of the earth. Under steam, even if they go no faster, ships may yet get farther toward the port of destination in a given time because the winds and currents may be disregarded, and they may be navigated over the oceans along great circles of the earth. The increasing recognition among mariners of the sound principle of conducting a ship along the arc of the great circle joining the points of departure and destination and the expanding sense of the advantages to be gained by a knowledge of this branch of nautical science have greatly heightened the value of methods which place the benefits of the knowledge and use of the great circle track at the service of the mariner without the labor of the calculations which are necessary to find the series of courses to be steered. Inasmuch as greatcircle courses alter continuously in proceeding along the track, it becomes necessary to know the latitude and longitude of the ship in order to determine the course to be followed. At the present day there are convenient means for determining at sea the longitude as well as the latitude, but before the early part of the present century these means did not exist, and great-circle sailing was impracticable. The general lack of the application of the principles of the great circle in later times, and even in the present generation, seems to have resulted not from the want of recognizing that the shortest distance between any two places on the earth's surface is the distance along the arc of the great circle passing between them, nor that the great-circle course is the only true course and that the courses in Mercator and parallel sailing are circuitous, nor yet to a due appreciation of the advantages to be gained by a knowledge of the great-circle course as a means for obtaining the most advantageous track in windward sailing; but to the tedious operations which have been necessary, and to the want of concise methods for rendering these benefits readily available. The solution, every time the course must be determined, of a spherical triangle in which the two sides and the included angle are given is a formidable operation for a mariner as compared with the measurement on a compass diagram of the direction of the straight line representing the circuitous path of the ship's track on the Mercator chart. At page 662 of the ninth edition of a work on Practical Navigation by Captain Lecky, of the Royal Naval Reserve of Great Britain, there is a section entitled 'Great Circle Courses found from Burwood's Tables,' which has doubtless been read with profit by thousands, for it states that "to find the great-circle courses from the azimuth tables you have only to regard the latitude of the port bound to as declination, and the difference of longitude, turned into time, as the hour-angle. The latitude of the ship you take from the top of the page as usual." But the author goes on to remark that, as Burwood's solar azimuth tables extend only to twenty-three degrees of declination, this ready-made method is only applicable when the place of destination is within the tropics. It may be of value, therefore, to point out that the solar-azimuth tables are universally applicable for finding great-circle courses, because all great circles pass into the tropics, and, if the problem of finding the courses is with reference to a great-circle track between a point of departure and a point of destination, both lying outside of the tropics, it is only necessary to find a point lying on the prolongation of the great-circle are beyond the point of actual destination and within the tropics, and treat this point as the place of destination in finding the courses. The longitude of the selected point within the tropics may be found without any calculation by simply prolonging the straight line representing the great circle upon a gnomonic chart. By this combination of the gnomonic chart and the azimuth tables the courses upon a great circle track may be determined with very great facility. To illustrate, take the problem of finding the initial course on a voyage by the great circle route from Bergen, in latitude 60° N. and longitude 5° E., to the Strait of Belle Isle, in latitude 52° 1' 2" N. and longitude 55° W. On a copy of a gnomonic chart, such as Godfray's, draw a straight line between the geographical positions above stated and extend it beyond the latter into the tropics. It will be found to intersect the 20th degree parallel of latitude in longi tude 90° W., or 95° from the meridian of the point of departure. Entering the azimuth table at latitude 60°, under declination 20°, and opposite hour-angle 95° or 6h. 20m., we find the required course to be N. 75° 31' W. G. W. LITTLEHALES. SOME NEW AMERICAN FOSSIL FISHES.* THE following new occurrences of fossil fishes were reported: (1) A species of Cladodus, scarcely distinguishable from C. striatus Ag. in the Corniferous Limestone of Ohio. (2) Thelodus-like scales from same horizon. (3) A pair of naturally associated pectoral spines of Macharacanthus from the Hamilton, near Buffalo, N. Y. (4) A ptychopterygian pectoral fin from Naples Shale of the same locality. (5) Two new species of Diplodus from Upper Devonian near Chicago, Ill. (6) Teeth of Phabodus from Keokuk Limestone of Iowa and Permian of Nebraska. (7) Largest known spine of Stethacanthus (length over 35 cm.) from Keokuk Group, Iowa. (8) A complete fin, spines and shagreen scales of a new and very large species of Acanthodes, a genus not hitherto met with in the United States, from Coal Measures of Mazon Creek, Ill. (9) Pholidophorus americanus sp. nov., also belonging to a genus new to this country, founded on very perfect material discovered by N. H. Darton, of the U. S. Geological Survey, in the Jura of the Black Hills, South Dakota. Photographs of the new Jurassic fishes were exhibited and their specific characters summarized as follows: Gracefully fusiform, upwards of 15 cm. long, the head forming about one-fourth the total length and slightly less than maximum depth of trunk; dorsal arising behind pelvic fins; scales not serrated, thin, smooth, nearly rhomboidal, overlapping; flank series not *Abstract of a paper read before the Boston Society of Natural History, March 15, 1899. especially deepened. This places them among the more primitive members of the genus, and hence would seem to indicate a Lower Jurassic horizon. The distribution of American Devonian fishes was discussed with reference to those of other countries. During the Lower Devonian there was none, and in the Upper scarcely any intermingling of United States and Canadian vertebrate faunas, but those of Canada and Great Britain belonged to a distinct province. Corniferous fishes of Ohio and New York are most nearly related to those of the Middle Devonian of continental Europe, especially the Eifel, Bohemia, etc. The Hamilton faunas of New York and the Mississippian region, including Manitoba, are the direct successors of the Corniferous, but the Chemung of both eastern and western regions (or its equivalent) contains a remarkable mixture of indigenous types and intruders from all directions. Intercommunication between eastern Canada and Great Britain, Spitzbergen, etc., became general for the first time during this period. The transition between Devonian and Carboniferous faunæ is now known to be more gradual than was formerly supposed. The only natural basis of family classification among Arthrodires was held to be through comparison of the sutures of cranial and dorsal shields, the differences in dentition being of only secondary importance. Degeneracy of the latter in Titanichthys, etc., is paralleled by that in certain toothless whales (Mesoplodon, etc.). Cranial osteology of Homosteus and Heterosteus compel their removal from Coccosteida to form a separate family called Homosteida. In this family the so-called antero-dorso-lateral sponds to the like-named element in Dinichthys and Titanichthys plus the clavicular. The latter plate functioned as a support for the gills, and hence may be interpreted as a modified branchiostegal apparatus, but in corre no sense as a part of the shoulder-girdle. There is no evidence that any of the Arthrodires possessed pectoral fins. The obvious resemblance of this group to Ostracoderms, with implied relationship, is lost sight of through its removal by Woodward to the Dipnoi, and there seems to be sufficient evidence for regarding the Arthrodira as a distinct sub-class, of equal rank with Lung-fishes, Teleostomi, etc., as already suggested by Dean. CHARLES R. EASTMAN. RAPIDITY OF SAND-PLAIN GROWTH.* THE undisturbed character of the stratified deposits making up the sand-plains, taken in connection with the absence, or at most, the very slight development of constructional back-sets, indicates, as was early pointed out by Davis, a stationary ice margin during the period of deposition. It follows, therefore, that their formation must have been extremely rapid, and the natural conclusion is that they represent the deposits of a single summer's period of melting, an interval not over eight months in length. It occurred to me that a calculation based upon the conditions now existing in the large glaciers of Alaska might give some indication as to the probability of such estimates, or at least would be of interest in this connection. To make this calculation it is simply necessary to divide the bulk of the sediments by the daily discharge of detritus by the glacial stream which deposited them. This involves factors which are usually very difficult to determine, but at the sand-plain near the railroad station at Barrington, R. I., the conditions are almost ideally perfect, and admit of the determination with considerable accuracy of both the bulk of *Abstract of paper read before Boston Society of Natural History, February 15, 1899. the sediment and the size and velocity of the stream transporting it. Owing to the fact that observations as to the amounts of the fine clay-like detritus of glacial streams are more numerous and reliable than those upon the coarser material, the bulk of the contemporaneous clays was taken as a basis of calculation, rather than the sand-plain itself. In estimating the load of the glacial stream, I have taken the maximum value of 13 grams per liter, given by Reid for the Muir Glacier (the highest value on record), as the one which, in all probability, would most nearly correspond to the load of a glacial stream during the closing stages of the continental ice sheet. At the time of the formation of the Barrington clays the land stood at a level of at least forty feet below that at present existing, and the deposition took place in an inclosed bay, having the ice sheet as its northern boundary, a ridge of till and modified drift for its eastern boundary, and an earlier sand-plain as its southern boundary. On the west was a broad and deep opening, connecting with Narragansett Bay, and admitting of a complete commingling of the salt and fresh waters. Into this inclosed bay flowed a stream with a width, as indicated by its esker, of 150 feet, a depth of some 20 feet, and an average velocity of not over 5 feet per second. On the assumption that the amount of sediment was 13 grams per liter, the daily discharge of clayey material would have been some 526,500 tons per day. Experiments recently conducted by Professor W. O. Crosby in connection with professional work for the Metropolitan Water Board of Massachusetts, the results of which he has kindly placed at my disposal, indicate that material such as the clay beds are essentially composed of, i.e., quartz-flour, settles with great rapidity, and it can be shown that practically the entire amount of sediment brought in by the glacial stream must have been deposited within the inclosed bay described. The clays cover about a square mile in area, have a maximum thickness of 60 feet, and a total bulk of 95,300,000 tons. Dividing this bulk by the daily discharge of sediment by the glacial stream (526,500 tons), the time of deposition of the clays is indicated to have been 181 days, or almost exactly six months. The Barrington deposits probably represent very nearly average conditions; hence a period of six months seems a fair estimate of time for the formation of a simple sandplain of moderate size. In the case of large plains, with areas of several or many square miles, the period of deposition may be considered as extending over more than one season of melting, there being in the meantime either no retreat of the ice margin or a retreat so slight that the intervening space was completely filled and the sand-plains united into a single compound plain. MYRON L. FULLER. PROPOSED SURVEY OF THE NILE.* THE Egyptian government has agreed to undertake a survey of the Nile with the object of determining the species of fishes inhabiting its waters. It is due in the first instance to the efforts and energetic action of Dr. John Anderson, F.R.S., who has already done so much to enlarge our knowledge of the fauna of Egypt that this important project, to which so much scientific interest is attached, has now taken definite shape. A memorandum prepared by him, setting forth his proposals for the survey and the lines of his scheme for carrying it out, received the approval of Lord Lister, President of the Royal Society; Professor E. Ray Lankester, Director of the Natural History Departments of the British Museum; Dr. A. Günther, President of the Linnæan Society, and Mr. P. L. Sclater, Secretary of the *From the London Times. Zoological Society, and was then forwarded by him to Lord Cromer, to be submitted to the Egyptian government, with a strong recommendation for its favorable consideration from these eminent scientific men. The Trustees of the British Museum furthermore gave the scheme their powerful and influential support, and intimated their willingness to assist in a practical manner by undertaking to supply the necessary collecting-boxes, with alcohol to fill them. An essential feature of the scheme is that the fishes collected are to be sent to London to be studied and determined by Mr. Boulenger, the ichthyologist on the staff of the Museum, and the Trustees have, it is understood, agreed to give him every facility for doing this, thus practically placing the services of their officer at the disposal of the Egyptian government for the purpose for the three years which it is estimated will be required to accomplish the survey. Our knowledge of the fishes of the Nile appears to be very imperfect. It may be said to have taken its origin in 1750, when Hasselquist described thirteen species found in the Deltaic area or in its immediate proximity. In 1847 sixty probably represented the number of known species. In 1861-63 Petherick made, at Dr. Günther's request, a collection of fishes from the Nile for the British Museum. The specimens were obtained at Cairo, Khartum and Gondokoro, and were described by Dr. Günther in an appendix to Petherick's 'Travels,' published in 1889. The collection contained eighteen new additions to the fauna, and raised the number of known species to eighty-two. Since 1869 the fishes of the Nile have been almost completely neglected. At present about ninety species are known to inhabit the river, but this number, considering the vast extent of its waterway and the very diverse physical conditions which characterize many parts of its course, cannot be considered as at all approaching finality. The collections hitherto made from the Nile have principally been obtained from below the First Cataract; indeed, Rüppell and Petherick are the only two collectors who had opportunities to investigate the river above Assuan. The former distinguished traveler and naturalist largely collected in lower Egypt, and not a few of Petherick's specimens were from the same region. In Dr. Günther's account of this collection only six species were distinctly recorded as coming from Gondokoro, Khartum and the White Nile, while thirteen, besides the foregoing six, species were stated to belong properly to the reach of the Nile above the Sixth Cataract. Here it may be observed that, while we possess a fragmentary knowledge of the species from Khartum southwards, the immense tract of the Nile from the First to the Sixth Cataract remains practically untouched. Morever, as within the next few years a change will be effected in the distribution of the Nile waters by the construction of the controlling powers now in course of erection at Phila and Assiut, and as other similar structures or dams are likely to follow towards the south, all of which are certain ultimately to limit more or less the range of certain species of fishes, it is much to be desired that, before any of these triumphs of the Department of Irrigation have been completed, we should be placed in possession of the main features and present condition of the piscine flora of the great reaches of the river. The present time is also extremely opportune for the commencement of the proposed investigation, since the authorities of the Congo Free State have satisfactorily inaugurated a survey of the Congo. Mr. G. A. Boulenger has been entrusted, with the sanction of the Trustees of the British Museum, with the description of the fishes of the Congo for the Congo Free State, and, as his services will be at the disposal of the |