July 31, 1891.] 



SCIENCE. 



65 



case of platinum. The silver behaved the same as gold, the 

 metal deposited freely, and the vacuum was easily kept at a 

 dark space of six millimetres by the very occasional admis- 

 sion of a trace of air. In twenty hours nearly three grains 

 ,of silver were volatilized. The deposit of silver was de- 

 tached without difficulty from the glass in the form of bright 

 foil. 



THE METEOROLOGICAL RESULTS OF THE " CHAL- 

 LENGER" EXPEDITION.' 



SBEDfa that water covers nearly three-fourths of the surface of 

 the globe, and exercises an important influence on the tempera- 

 ture of the air above it, and, by the intervention of winds, extends 

 that influence over the land surfaces, it was impossible to give a 

 satisfactory account of the meteorology of the earth in the absence 

 of records of a complete series of observations taken in the open 

 ocean. It was, therefore, of the utmost importance that the rec- 

 ords of the "Challenger" expedition should be thoroughly di- 

 gested, and this work Dr. Buchan, after seven years' labor, brought 

 to a conclusion rather more than a year ago. In addition to the 

 results of the " Challenger " observations, he also made use of 

 records of temperature, atmospheric pressure, etc., received from 

 a large number of stations in all parts of the world. Some of the 

 most striking points in the report are given in an address to the 

 Royal Geographical Society, published in the Proceedings for 

 March and accompanied by four maps, of which two show the 

 distribution of temperature and atmospheric pressure, respectively, 

 for the month of January, and the other two the same phenomena 

 for July. These are reproductions of some of the fifty-two maps 

 annexed to the report. 



One important factthatthe "Challenger" observations revealed 

 is, that the daily variation of the temperature on the surface of 

 the ocean away from land is very small, nowhere exceeding a de- 

 gree between latitudes 40° north and 40° south, and falling to 

 one-fifth of a degree in the high latitudes. The temperature of 

 the air was found to have a range about three to fotu: times as 

 great as that of the water below. In the Southern Ocean, at 

 latitude 63°, it was 0.8 of a degree, or four times as great as that 

 of the sea in the same region. Over the open sea the humidity 

 curve closely follows that of the temperature, falling to a mini- 

 mum at four o'clock in the morning and rising to a maximum at 

 two in the afternoon ; but near land a second minimum occurs from 

 about 10 AM. to 2 P.M. At this time, the land being heated, a 

 current rushes in from the sea to take the place of the hot air that 

 rises from it, and dry air from the upper regions of the atmos- 

 phere descends over the ocean. Over the open sea the barometer, 

 though removed from the disturbing infiuence of land, shows as 

 marked oscillations as over land where the diurnal variation of 

 temperature is great. The cause must be sought in the daily 

 changes in the temperature and humidity of the air produced 

 through all its height by solar and terrestrial radiation. 



Another important fact is that, latitude for latitude, the ampli- 

 tude of the barometric oscillations is larger in an atmosphere 

 highly charged with aqueous vapor than in a dry one. In the 

 anticyclonic regions of the Atlantic and Pacific, the barometer 

 falls only about 0.035 inches from the morning maximum to the 

 afternoon minimum. Since pressure remains high, though cur- 

 rents of air are constantly flowing out from these regions in all 

 directions over the surface of the ocean, it follows that the dry 

 air from above must descend into their centres. These anticy- 

 clonic regions play a most important part in regulating the cli- 

 mates of the neighboring continents. The four principal lie in 

 the Atlantic and Pacific, at about latitudes 36' north and south, 

 and appear in all the monthly charts, with the exception of the 

 North Atlantic region, which is absent in the month of January 

 only. The absolutely highest mean pressure for any month, 

 about 30.5 inches, is to be found in central Asia in the month of 

 January. Here, to the south of Lake Baikal, is the centre of a 

 great anticyclone, covering a large part of Eurasia, from which 

 south and south-west winds blow over Russia and western Siberia, 

 > From the Scottish Oeographical Magazine for July. 



raising the temperature of these countries. Their effect may be 

 seen on the temperature chart, on which the isothermals run 

 nearly north and south. 



Another example of the effect of pressure on climate may be 

 taken from the low-pressure system in the North Atlantic, where 

 the lowest mean pressure of 29.5 inches occurs between Iceland 

 and the south of Greenland. This system gives rise in winter to 

 south westerly winds in western Europe, and north-westerly winds 

 over North America. While, therefore, the temperature of the 

 former is abnormally raised by winds from lower latitudes, that 

 of the latter is lowered by cold breezes from the Arctic regions. 

 Hence, the temperature of the coast of Labrador is only — 13°, 

 while on the same parallel in Mid-Atlantic it is 45°, or 58° higher. 



The influence of other cyclonic and anticyclonic areas is dis- 

 cussed in Dr. Buchan's article. In reference to the drawing of 

 isobars, the author gives a warning against the use of observations 

 in steep and confined valleys, where descending cold currents at 

 night and ascending warm currents in the afternoon unduly raise 

 and depress the barometer alternately. Thus, in the Valley of 

 TOnset. in Norway, the mean is 39.95 inches, while at Dovre, 

 situated at about the same elevation but separated from Tonset by 

 a broad range of mountains, it is 29,87 inches. 



Lastly, a few figures must be quoted regarding the velocity of 

 the wind. This the "Challenger" observations showed to be 

 greater over the open sea than near land, the mean difference be- 

 ing from four to five miles per hour. It is greatest over the 

 Southern Ocean (23 miles per hour) and least over the North Pa- 

 cific (15 miles). The curves on the open sea show a very slight 

 diurnal variation, but near land they exhibit a distinct minimum 

 between 3 and 4 a.m., and a maximum from noon to 4 p.m. The 

 dUference between the velocities on sea and land is greatest at 4 

 A.M., and gradually falls to a minimum at 2 p.m., demonstrating 

 the effect of the land in reducing the velocity by friction, and the 

 fact that this effect is, in some way or other, partially counter- 

 acted by the heating of the surface of the land. Such are a few 

 of the important results pointed out in Dr. Buchan's paper, 

 which is so full of valuable information that no abstract can do it 

 justice. 



THE NEW LAKE IN THE COLORADO DESERT. 



Speaking of the lake recently formed in the Colorado desert, in 

 the southern part of California, by the overflow of the Colorado 

 River, Major J. W. Powell, director of the United States Geologi- 

 cal Survey, recently gave a reporter of the New York Times some 

 interesting facts. 



"The traditions of the Indians are by no means the onlj' evi- 

 dence that this basin has been filled, wholly or partially, before," 

 said Major Powell. " Since the delta was formed, and that por- 

 tion of the Gulf of California was cut off and left to evaporate 

 under the terrific heat of the sun, the Colorado has been playing 

 pranks of this sort on several occasions. Along the hills which 

 form the sides of this basin there are shoremarks which indicate 

 that at different times the basin has been flooded to different 

 heights, and then, when the river cut back through its old chan- 

 nel, evaporatian has again changed the lake to a parched desert. 

 Along these shore-lines shells have been found which confirm this 

 theory. The action of the Colorado in cutting new mouths for 

 itself and then stopping them up is comparatively rapid because 

 of the quantity of silt which the stream carries. It is not unlikely 

 that the supposed traditions of the Indians are facts within the 

 memory of some of the older ones of the scattering bands that 

 live on the hillsides along the basin, for indications are that the 

 valley has been inundated within fifty years, and certainly it has 

 been at least once or twice since this continent was discovered. 



" There is no immediate danger of the basin being filled, be- 

 cause it requires a large volume of water to fill it to the river 

 level, and the evaporation is something wonderful. At the pres- 

 ent time, according to reports, only a fraction of the water in the 

 Colorado is fiowing through this new outlet. It is possible that 

 the channel may be enlarged as the stream continues to flow 

 through it, so that all the water in the river will pour into the 

 basin. Even if that were to happen the evaporation is great 



