375 



It will be seen from the above tables that, at the period .of blooming, 

 plants have reached their maximum in the appropriation of nitrogen, 

 iron, phosphoric acid, potassa, magnesia, and soda, and that silica is in- 

 creased during the period of ripening, and lime also (as shown in the 

 first table) ai)pears to increase until within fifteen days of maturity. 

 This is Avhat might be expected, for at that period the straw is becom- 

 ing more solid by the thickening of its enamel, which is composed chiefly 

 of silicate of lime. 



Another curious fact, which these experiments teach, is that not only 

 does the plant cease to appropriate mineral elements (except silica) in 

 the last thirty days of its growth, but that it actually returns to the 

 soil, as unnecessary for its purposes, a considerable portion ^of that which 

 has already been absorbed. A crop removed at the period of flowering- 

 will take more from the soil than it would if permitted to ripen fully 

 before cutting. 



« 



Scientific notes. — Increased consumption of sugar. — Though the 

 manufacture of sugar was commenced in the West Indies early in the 

 sixteenth century, yet its use in domestic economy did not become 

 general in Europe or America before the beginning of the last century. 

 In the year 1700, only 10,000 tons were used in Great Britain, though 

 the English were at that time the leading manufacturers of sugar. The 

 consumption of sugar in the British Islands in the year 1870 is stated 

 at 600,000 tons. In this country the consumption of sugar is steadily 

 increasing. Since the close of the late war, the ratio of increase has 

 been about 10 per cent, annually, and in the year 1871 the sugar con- 

 sumed in the United States amounted to 700,000 tons, an increase of 15 

 per cent, on the preceding year. This Is the largest consumption of 

 sugar, in proportion to the«population, found in any nation on the globe. 

 A very small proportion of the sugar consumed in the United States is 

 produced within our own territory, while in Europe the production of 

 sugar is rapidly increasing and bids fair soon to render the principal 

 nations of that quarter independent of the tropical regions in regard to the 

 supply of sugar. Since the year 1850, the production of sugar from beets 

 in France has risen from 00,000 tons to 300,000; in Austria, from 10,000 

 to 80,000 tons; and Russia, where beet-culture w^as introduced since 1850, 

 now produces 100,000 tons of sugar. The increased consumption of 

 sugar may be taken as the evidence of an advance toward a higher civ- 

 ilization. 



Respiration of fishes. — N. Grehaut (Comptes-rendus, Ixxvi, 621) 

 reports a series of experiments on the breathing of fishes, important, as 

 being in the line of those of Humbdldt on the same subject, and reach- 

 ing results, in some respects, at variance with his. Grehaut reportsthat 

 fishes give oft' a volume of carbonic acid(anhydride) equal to the volume 

 of oxygen exhaled. Humbolt states it at only four-fifths of this. Again, 

 Grehaut afiirms that nitrogen is increased in the air exhaled, while Hum- 

 boldt reports it as diminished. We are not told, how^ever, that the experi- 

 ments were made on the same kind of fishes and under similar circum- 

 stances. • 



These experiments prove that fishes can remove the whole of the oxy- 

 gen dissolved in water and can even deprive arterial blood of its oxygen 

 when the same is mixed with the water which the fish inhales. The 

 writer regards this fact as of importance in general physiology, as illus- 

 trating the mode in which oxygenation of the blood is effected in the 

 mammalian fetus, through the maternal placenta. 



