Billeder på siden
PDF
ePub

coe, writing on the 16th of January, 1831 (on approximately the sixtieth to the sixty-third parallel of latitude), states that "the temperature of the water was 34°, of the air in the shade 45°, in the sun 77°, with a corresponding general warmth to the feelings of the crew." The highest reading of the thermometer for the month of January was noted by Kristensen to be 40° F., and the lowest 27°; fifty-three years earlier (1842) Ross found for the same month 39° and 27.5°, with a mean of 32°, thus indicating an equality almost without fluctuation.

The fact that the high south has not yet been penetrated in the winter months leaves us in uncertainty as to the winter temperatures that may prevail there; but some indications of this temperature are to be found in the records which have been obtained in the circumantarctic tract. Ross registered the absolute minimum, for the year 1842, in the Falkland Islands to be only 19.2°; but still more significant is the reading of the minimum thermometer which was left by Forest in 1829, on Deception Island, and recovered by Captain W. H. Smiley (as reported by Wilkes) in 1842, or after an interval of thirteen years. The registry was found to be -5° F. It is true that Deception Island lies without the Antarctic Circle, and that its insular condition must measurably reduce the rigors of a winter climate; but even these conditions permit us to form some just estimate of what "lies beyond,” and of making some interesting comparisons with corresponding localities (so far as latitude is concerned) in the north. Thus, at Fort Reliance, in North America, the mercury descends to 70° F., and at Yakutsk, in Siberia, nearly one degree nearer to the equator, to — 75°; and if we are to fully believe the registry at Verkhojansk, for the winter of 1893, the unprecedently low temperature of 90° was reached. But one need not make comparisons with these especially cold localities, as it is well known that at the sites of the principal commercial cities of the world the mercury at times descends to from -5° to -15° (New York and Philadelphia, 1866, 1895). On January 23, 1823, the mercury in Berlin descended to -31° F., and in Paris on January 25, 1795, to- 21°. It is perhaps just to conclude from these and other facts that the extreme winter climate of the Austral Ocean, on or about latitude 63° south, is no more severe than that of southern

[ocr errors]

France, and hardly more so than that of northern Italy. And while it is doubtless true that a considerably lower marking of the thermometer would be found in the much more extreme regions of the south, or nearer to the pole, it is practically certain that nothing comparable to the cold of the opposite face of the globe exists."

R. E. D.

The Lakes of Florida.-" The peninsula naturally separates into three divisions: the middle portion, which comprises the beautiful lake region; the west coast, which slopes away from the high ridge to the Gulf of Mexico; and the east coast, whose sandy levels are protected from the Atlantic by the great coquina atoll, extending from the mouth of the St. Johns river to the shores of Lake Worth. Each of these divisions differs wholly from the others, presenting conditions and characteristics peculiar to itself.

Middle Florida is a broad ridge which reaches, at places, an elevation of nearly 250 feet. The soil is, for the most part, sandy, but, like that of the State in general, it contains a sufficient quantity of phosphate to render it fertile. Forests of pine are everywhere. Here and there a cypress swamp varies the scene, and now and then a palmetto hummock suggests the approach of the tropics, It is in this division the lake region is found. Dotting the landscape, like jewels of crystal in a field of green, are numberless lakes, varying in size from a gem-like lakelet to the broad expanse of Okeechobee. Within a radius of 5 miles from Winter Haven 100 have been counted, and within 7 miles of Orlando there are known to be 150. With Gainsville as its northern limit, and including lake Okeechobee on the south, this region contains, as a conservative estimate, at least 30,000 of these lakes and lakelets."National Geographic Magazine, Dec., 1896.

66

The Sage Plains of Oregon.-The vegetation of the great plains in Oregon between the Bitter Root and Cascade Mountains 'consists primarily of sage brush, a shrub three to six feet high, closely related to the wormwood of Europe and having, in common with that plant, a light gray color and a strongly aromatic odor. Away from stream beds and sinks and the shores of lakes, sage bush covers the whole country like a gray mantle and constitutes probably nine-tenths of the total vegetation. It is a plant, the

herbage of which is eaten by but few animals and by those only in starvation times, one that will grow with little moisture and will stand the widest range of temperature. Sage brush gives to the country its character. A level stretch is known as a sage plain; the grouse which live there are known as sage hens; the fuel of the region is sage brush; the odor upon the atmosphere is that of sage brush."-National Geographic Magazine, Dec., 1896.

New Jersey Forests and their Effects.-Much debate has arisen within a few years concerning the influence of forests upon floods and droughts and upon other conditions of streams determining the success of man in agriculture or commerce.

The recent report on forestry of the State of New Jersey brings out most forcibly the value of large forested areas in the catchment basins of water for large cities. Cultivation necessarily means presence of population that would naturally pollute the water of streams, and also means the loosening of soil, so that the draining streams would be roily. The rivers in the northeast highlands of New Jersey are in a forested area and are much more clear and drinkable than the rivers to the southwest, where cultivation is more extended.

The flow of streams is also more regular from the forested than from the barren or cultivated watershed. Floods are heavy and frequent under the latter conditions. "The economic importance of this lies in the greater value of forested streams for water power and the smaller storage reservoirs needed therein to furnish a given supply of water to cities. Illustrative of this the Passaic river (forested) will furnish for nine months of the year from 100 square miles of watershed, 45 horse power on 10 ft. fall, whereas the Raritan (cultivated) will furnish but 41 and the barren watershed 28. During the other three months the Passaic will furnish an average of 36, the Raritan 32, and the barren watershed 20 horse power." R. E. D.

Maps in History.-Mr. Henry Gannett, of the United States Geological Survey, has an interesting article in the Bulletin of the American Geographical Society, Vol. XXVIII., No. 3, entitled a Graphic History of the United States. In it he gives, by a series of maps, the history of the changes of territory of the different

States of the Union. For instance, New York is shown both before and after its reduction by the separation of Vermont in 1791. The most interesting cases given are those of States which formally claimed land indefinitely westward. For instance, Kentucky was cut from Virginia in 1782; West Virginia in 1863. Georgia was decreased in 1802 by separation of all of Alabama and Mississippi lying north of 31st parallel. Louisiana comprised all the basin of Mississippi on the west of the stream, south to head of Arkansas in Colorado, eastward to 100th meridian and south to Red river, and down this river to present confines of Louisiana, which was followed to Gulf. Indiana once included Illinois, Wisconsin, Michigan and part of Minnesota. Other States have suffered similar losses, all of which are interesting and the understanding of which is necessary to one who would give some meaning to geographic boundaries as they are mechanically memorized in many schools. R. E. D.

Recent Geographic Changes in Switzerland.-Prof. Edward Brückner has recently described in Petermann's Mitteilungen the very interesting results of a comparative study of a remarkable map of the seventeenth century and one of the Swiss survey maps of to-day. In 1667, Mr. J. C. Gyger completed his map of a part of the Alpine region extending from the Rhine on the north to the Reuss on the south, and including the whole of the canton of Zürich in Switzerland. The map was on an unusually large scale for that time. The scale was 1:32,000, or one inch on the map for about a half mile in nature. He worked compass in hand, paced his distances, and was very careful and laborious in his survey. He gave a great deal of time for thirtyseven years to his map. He was the first to use lights and shadows to indicate and contrast mountain slopes. Two copies of his map, both signed by him, are extant, and they still excite the admiration of cartographers for the wonderful accuracy with which they depict topography. Until this century the Gyger map was regarded as the best cartographic delineation of the Zürich canton. Small parts of it have been published with corresponding sections of the present surveys, to show the high standard of accuracy Mr. Gyger attained.

Mr. H. Walser has carried out, in the Geographical Institute of the University of Berne, the comparison between the Gyger map and that of the present day. Mr. Gyger carefully showed every lake, large and small, in the canton and sharply distinguished the lakes from the swamps. His map showed 149 lakes in the canton. Of these, no less than seventy-three are not found on the present maps. These lakes, as Mr. Walser points out, one by one have become extinct. They were all small, most of them having an area of less than twenty-five acres. The area of sixteen other lakes is now much reduced, and twenty others are somewhat smaller than in the seventeenth century. Forty lakes have undergone no important change.

Mr. Walser has ascertained by observation the causes of the shrinkage or disappearance of fifty-four of these lakes. The farmers, in their efforts to secure more meadow land, have played an important rôle. They have drained quite a number of the lakes and turned their beds into hay farms or pasture lands. Of course, in geological time, all lakes are drained by the natural cutting down of their outlets, but, on account of the unimportant slope of the outlet channels of these particular lakes, the deepening of the channels was very slow, and this form of lake effacement seems to have cut no figure.

The effect of two other natural causes, however, are very evident. One was the silting up of the lakes by the deposit of sediment, and the other, and more important, the gradual encroachment of plant life in the lakes, which finally completely filled them, the decay of vegetation forming soil, and thus the lakes were gradually extinguished. Some of the lakes are still undergoing this process, the carpet of plants extending all around the shores, while a little water surface is still visible in the center. The deposition of sediment and the growth of plants which finally obliterated these little lakes were, of course, supplemented, as Mr. Walser says, by the human activities that, in the past century, largely cut off the water supply that made and fed them.

Mr. Gyger very carefully showed the forests on his map, and the comparison that has now been made between the area of forests in the canton two centuries ago and at the present day is very interesting in view of the statement, often heard, that Europe is

« ForrigeFortsæt »