Ivi GENERAL SUMMARY OF SCIENTIFIC AND 



is quite sufficient to carry the wire to a depth of several 

 thousand fathoms, whereas \vith the hempen rope a ball 

 Aveighing* several lumdred pounds is necessary. 



Under the general head of Physical Geography we have 

 nothing of special interest to report, although attention has 

 been called to the influence of marine vegetation in enlarging 

 the coast-line, as shown in the Indian Ocean, especially in 

 the island of Sumatra, where the outgrowth of the mangroves 

 alonsr the shore results in the accumulation of other vecreta- 

 tion and the subsequent formation of soil, and the reclama- 

 tion of a considerable extent of land from the sea. This is 

 seen elsewhere, and may be noted on a large scale in the isl- 

 ands off the coast of Florida. 



Numerous articles have appeared during the j^ear, show- 

 ino' the relation of forests to rain-falL and an earnest effort 

 has been made to induce the State of New York to take pos- 

 session, by means suggested, of the head waters of the Hud- 

 son River in the Adirondack region, and to prevent the tim- 

 ber from beinc; removed. It is uroed that the continuance 

 of the navigability of the Hudson is intimately connected 

 with this precautionary measure, the experience of other 

 parts of the world showing that, even although there may be 

 no absolute variation in the rain-fall in a given region, its 

 denudation of forest growth causes the water to run off very 

 rapidly, producing dangerous freshets, to be followed by a pe- 

 riod of extreme low water; whereas nnder normal conditions 

 the moisture is held for a time in the forest soil as in a sjDonge, 

 and gives off its supply gradually and uniformly throughout 

 the year. The experience of the island of Santa Cruz is ad- 

 duced as a warninc: of the results followino; the removal of 

 forests, in respect to which it is stated that for many years, 

 Avhile covered with trees, the whole of this island was fertile 

 and liabitable, whereas in consequence of the gradual de- 

 struction of the forests the island is rapidly drying np, and, 

 unless precautionary steps are taken, bids lair to become an 

 uninhabitable desert. 



As a preliminary to the subject of Explorations and Re- 

 searches^ we may refer to several communications which have 

 appeared in reference to great areas of the earth's surface 

 at present unexplored, a Avriter in The Academy remarking 

 that of these there are four, of great extent, never traversed 



