43 



THE POPULAR SCIENCE MONTHLY. 



and begin to bear in about five or six years, 

 yielding then from twenty to thirty oranges 

 each, and increasing their crop for ten years 

 till in full bearing, when they produce from 

 two to three hundred, and, in most favorable 

 circumstances, one thousand oranges a year. 

 The trees remain fruitful for more than thirty 

 years. The cost of cultivating and attending 

 a thousand orange-trees in Brazil is esti- 

 mated at about seventy dollars a year. 



Climate and Vegetation. In a paper on 

 the relations of climate and vegetation, M. 

 M. Bergsman, of Flushing, reaches the con- 

 clusion that a mixed climate, with relatively 

 mild winters and warm, sunny summers, is 

 the best suited for the vegetation of the 

 temperate zone. Corn can be cultivated 

 only as a green vegetable in England ; is 

 profitable in Western Europe only to 46, 

 and in the valley of the Rhine to 49, but 

 in certain regions of North America to 51, 

 and even under the Polar Circle in Norway, 

 where it has the sun day and night. Plants 

 much resembling those of Central Europe 

 grow in the Amour region of Siberia, where 

 precipitation occurs only in summer, and 

 that season is warm, in the face of a winter 

 temperature much lower than is observed in 

 the most northern parts of Lapland. Rad- 

 ishes, turnips, rape, and the potato grow as 

 far north as there are settlements, but in 

 the extreme north the potatoes are only as 

 large as walnuts, and the plant never blos- 

 soms in Greenland. When comparing ex- 

 treme continental climates with extreme sea 

 climates, the continental climate has the ad- 

 vantage. The extreme southern limit of 

 phanerogamous plants is in the South Shet- 

 land Islands, latitude 60 to 63 south, and 

 the last trace of vegetation, in cryptogams, 

 is found on Cockburn Island, 64 south. At 

 the same latitude in Northern Siberia is a 

 forest of very high coniferous trees. The 

 chief reason that corn can not be cultivated 

 in Siberia beyond 62, at Yakutsk, is on ac- 

 count of the constantly frozen condition of 

 the ground at a short distance beneath the 

 surface. In Europe, even, the climate of 

 the northern parts of the British Isles is not 

 suited for many vegetables and other culti- 

 vated plants. It is in Germany where almost 

 all the plants of the temperate zone and 

 those commonly cultivated can be found. 



Even in that country the summer tempera- 

 ture in general is only a few degrees above 

 that calculated for the latitude. Germany 

 is crossed in July by the isotherm of 68, 

 and Britain by that of 59, but the differ- 

 ence in vegetation is not caused by the dif- 

 ference of 9 in mean temperature, but by 

 the difference in the amount of sunshine. 



Denudation of the Continents. Mr. T. 

 Mellaid Reade, addressing the Liverpool 

 Geological Society on " The Denudation of 

 the Two Americas," showed that one hundred 

 and fifty million tons of matter in solution 

 are annually poured into the Gulf of Mexico 

 by the Mississippi River. This, it was esti- 

 mated, would reduce the time for the denu- 

 dation of one foot of land over the whole ba- 

 sin which time has hitherto been calculated 

 solely from the matter in suspension from 

 six thousand years to four thousand years- 

 Similar calculations were applied to the La 

 Plata, the Amazon, and the St. Lawrence ; 

 and Mr. Reade arrived at the result that 

 an average of one hundred tons per square 

 mile per annum is removed from the whole 

 American Continent. This agrees with re- 

 sults he had previously arrived at for Eu- 

 rope, from which it was inferred that the 

 whole of the land draining into the Atlan- 

 tic Ocean from America, Africa, Europe, and 

 Asia contributes matter in solution which, 

 if reduced to rock at two tons to the cubic 

 yard, would equal one cubic mile every six 

 years. 



Photographing Colors. Professor H. 

 W. Vogel has made a report of the final re- 

 sults of his researches on the means of pho- 

 tographing colored objects in their natural 

 shades. Sensitive plates are affected only 

 by the more refrangible rays, so that they 

 present totally unnatural and distorted pict- 

 ures, as to the shading, of colored objects. 

 Believing that the sensitive collodion is af- 

 fected only by such colors as are absorbed 

 by it, Professor Vogel's efforts have been 

 directed to making his plates sensitive to 

 less refrangible rays by alloying the silver 

 coating with a substance capable of absorb- 

 ing those rays. His experiment succeeded 

 with the natural colors, but he could not ob- 

 tain an effect with the duller artificial colors. 

 He then sought for organic substances pos- 



