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THE POPULAR SCIENCE MONTHLY. 



cial stratum, while the temperature of the 

 American coast is lowered by the surging 

 up against it of deep glacial underflow. The 

 fact, he says, comes out most clearly from 

 the Challenger soundings, which had been 

 suspected by the United States Coast Sur- 

 veyors, that the cold band which separates 

 the Gulf Stream from the United States 

 coast is really continuous with the cold 

 strata that lie at some depth beneath the 

 Gulf Stream, and this continuity explams 

 the presence of the cold band which was 

 previously wanting. For, as any flow of 

 water from the equator toward either pole 

 will tend toward the east in virtue of the 

 excess of easterly momentum it brings frOm 

 a part of the globe where its rotation was 

 rapid ; so any flow of water proceeding from 

 either pole toward the equator will tend 

 toward the west, in virtue of that deficiency 

 of easterly momentum which it derives from 

 a part of the globe where its rotation was 

 less rapid. In this surging upward of the 

 deeper and colder stratum lying beneath 

 the Gulf Stream, we have very distinct 

 evidence of its southerly movement. The 

 precisely similar cold band which has been 

 observed by Captain St. John to separate 

 the Kuro Li wo, or warm Japan current, 

 from the coast, may be fairly attributed to 

 the same cause. 



Action of Frost on the Position of Trees. 



— The elevation of the trunks of trees was 

 the subject of some observations by Mr. 

 Thomas Meehan at a recent meeting of the 

 Philadelphia Academy of Sciences. On a 

 previous occasion he had attributed this 

 elevation to the natural thickening of the 

 roots, which brought them in contact with 

 unyielding rock beneath, the necessary con- 

 sequence being that they would then lift the 

 entire tree. Since that time he has been 

 led to offer another explanation, viz., the 

 action of frost. Most trees standing by 

 themselves, he observed, have the collar of 

 much greater diameter than the trunk above, 

 and the upper portions of the roots, spring- 

 ing from about the collar, are considerably 

 above the surface of the ground. That this 

 is caused by the action of frost is rendered 

 probable by what we know of its action on 

 minor vegetation, what is called " drawing 

 out." When the land freezes, expansion 



ensues, drawing up with it the roots of 

 clover, and leaving of course a cavity from 

 which the root was drawn. At the first 

 thaw the Hquid, carrying earthy matter, 

 enters the cavity, and then the clover-root is 

 prevented from descending to its original 

 position. The same is true of trees. Roots, 

 heaved up by frost, find the cavity beneath 

 partially filled, and hence the tree will stand 

 a little higher than before. Dr. Latham, 

 State Botanist of Wisconsin, is of the opinion 

 that large trees blow over much more readily 

 than younger ones with the same, propor- 

 tional weight of head to development of 

 roots, chiefly because the older trees have 

 been drawn nearer to the surface. One of 

 the chief oflfices of the tap-roots is probably 

 to prevent the tree being lifted too high by 

 the frost. Dr. Meehan is inclined to think 

 that the trees of tropical climates have by 

 no means so great a development of tap- 

 roots as those of more northern regions. 

 This question he proposes to investigate 

 further. 



Topography of the Bed of the Pacific— 



Soundings made by the United States 

 Steamer Tuscarora, between San Diego, 

 Cal., and Honolulu, S. L, show this part of 

 the Pacific to be a basin with precipitous 

 sides and a comparatively level bottom. 

 In the first 100 miles west from San Diego, 

 there appear to be two valleys and two 

 peaks. The first valley is from 622 to 784 

 fathoms deep, the first peak 445 fathoms, 

 the second valley 955 fathoms, and the sec- 

 ond peak 566 fathoms. Thence a precipitous 

 fall takes place, giving, in latitude 81 °43' 

 north, longitude 119° 28' west (Greenwich), 

 115 miles from San Diego, a depth of 1,915 

 fathoms. After that there is a gentle 

 slope, with comparatively unimportant in- 

 terruptions, at the rate of three feet to the 

 mile, to the point of greatest depth, 3,054 

 fathoms, at a distance of about 400 miles 

 east of Honolulu. The sharpest elevation 

 is a rise about midway between the United 

 States and the Sandwich Islands, in lati- 

 tude 26° 30' north, longitude 127° 37' west, 

 the highest portion of which is 2,159 

 fathoms below the surface. At the next 

 cast of the lead the valley to the west of 

 this elevation took 2,650 fathoms. The 

 fall of the side of the basin, east of Honolulu, 



