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THE POPULAR SCIENCE MONTHLY. 



lated by the plant in the free state deter- 

 mined to apply infusorial earth to land sown 

 in wheat, and afterward with the microscope 

 to search for the siliceous shields of diato- 

 ruaeeae in the straw. Of course, if these 

 were to be found occurring in the plant with 

 the same forms which they have in the in- 

 fusorial earth, it is plain that they must 

 have been taken up by the plant and dis- 

 tributed through its system unaltered. The 

 event fully justified this conclusiou. The 

 straw having been treated with nitric acid, 

 the siliceous residuum was placed on the 

 field of the microscope, and was seen to 

 consist wholly of the siliceous shields of 

 diatomacea;, the same as found in the infu- 

 sorial earth, excepting that the larger disks 

 in their perfect form were absent evident- 

 ly because these disks were not sufficiently 

 minute to enter the root-capillaries. The 

 result of these investigations shows the 

 necessity of finely-divided silica in the soil ; 

 also, that simple or compound silicates are 

 useless as fertilizing agents. 



Forestry. The first of a series of papers 

 on " European and American Forestry," now 

 appearing in the Penn Monthly, contains a 

 brief history of " Deforestation," or devas- 

 tation of forests, in the Old World. The 

 subject is one that nearly concerns the in- 

 habitants of the United States, where the 

 process of deforestation advances with un- 

 paralleled rapidity. Among the many in- 

 stances quoted by the author of the evils 

 consequent on the denudation of woodlands 

 is that of Sicily, once the granary of Rome, 

 now almost a waste from the effects of for- 

 est devastation. The island has scarcely a 

 stream that lasts through the summer, and 

 few perennial springs. The soil has suffered 

 deplorably for want of sufficient irriga- 

 tion. Greece, in common with Asia Minor, 

 has been shorn of its original forests, and 

 its characteristic feature is represented in 

 steppes and unproductive barren wastes. 

 Of Spain it may be said that at one time 

 one-fifth of its surface was forest; now the 

 proportion is only nine per cent. Indiffer- 

 ent portions of the country noble forests 

 still exist ; but, on the whole, the destruc- 

 tion of the useful woods has been indiscrim- 

 inate and improvident, and Spain, like all 

 other countries, has suffered under the 



abuse of that universal law according to 

 which soil and climate depend on the extent 

 of forest-land. 



Air-Bags for raising Ships. Prof St. 

 Claire, of Edinburgh University, in 1785 

 proposed the use of air-bags for the pur- 

 pose of raising sunken ships. In 1864 air- 

 bags were first practically applied for rais- 

 ing a steamer sunk in the lake of Bodcn ; in 

 this case the bags, owing to some defect, 

 gave way. The Alexandrovsky system, 

 perfected some ten years ago, has already 

 rendered good service to the Government 

 and commerce of Russia on several occa- 

 sions. The bags adopted in the Russian 

 Navy, as we learn from Engineering, are, 

 when inflated, of cylindrical form, measur- 

 ing twelve feet in diameter and twenty feet 

 in length. They are composed of three 

 layers of the thickest canvas saturated with 

 India-rubber. Their lifting power averages 

 sixty tons. In order to lift a vessel, several 

 chains are drawn by divers under her bot- 

 tom, and air-bags attached to the ends of 

 each of them as near the ship's bottom as 

 possible : the bags, being inflated by means 

 of air-pumps, cause the ship to rise. Before 

 pumping air into the bags, all the chains 

 are connected in a transverse direction, so 

 as to form one system, thus preventing the 

 pairs of bags from sliding off from beneath 

 the hull of the ship. As the vessel rises 

 the surrounding water-pressure decreases, 

 and the excess of air passes out through 

 safety-valves. 



Night - Habits of Fish. Mr. W. Saville 

 Kent had in the Manchester Aquarium a 

 number of young herrings, which were so 

 tame as readily to take their prepared 

 food from the hand of a keeper. But a 

 large number of the fishes were found 

 dead each morning, a fact which seemed in- 

 explicable, considering their quiet behavior 

 during the day. A night inspection, how- 

 ever, revealed the cause of this rapid de- 

 struction. It was found that the nocturnal 

 movements of the herring, at least in con- 

 finement, are altogether different from their 

 movements in daylight. In the latter case, 

 these movements are quiet and uuiform, the 

 fish swimming around their tank in one 

 shoal and one continuous stream. At night, 



