472 AGRICULTURAL REPORT. 



menccment of the year, it will be found that when the sum shall have reached 

 a certain figure the same phenomena of vegetation will be exhibited, such aa 

 foliation, blooming, and matunitiou of the fruit. 



Boussingault, that "prince of agronomical chemists," in whom combine the 

 successful farmer and the profound philosopher, whose " llural Economy" 

 should be studied by every farmer, and whose new "Agronomic" promises yet 

 more brightly to illumine his name, and the path of the scientific seeker for 

 "light — more light," revived the hypothesis of Reaumur and enlarged its ap- 

 plication. Many years' residence in South America, engaged in scientific 

 observation and research, where vegetation upon mountain sides appears under 

 almost every aspect and condition, combined with experience in the pursuits 

 of agriculture ou his larm at Brechelbronn, in Alsace, had taught him that if 

 we multiply the number of days — the length of time a summer plant endures — 

 by the mean temperature of this period, the product will be the same in all 

 countries and in all years. 



Baron Quetelet, of Brussels, styled by his countrymen "the Belgian Arago," 

 has experimented upon the amount of heat required by plants, and proposes 

 that it should be measured not by the simple product of the temperature of 

 the several days by the number of days required, but that the squares of the 

 mean temperatures should be employed in lieu of the daily mean. The younger 

 De Caudulle has, however, sought in vain in the researches of Quetelet and 

 others for any positive facts showing the direct advantages of the variations 

 of heat over continuous even temperatures, or for the evidence fully determin- 

 ing that one day having a mean of 20° centigi-ade, is of equal value with four 

 days having each a mean of 10^ centigrade, as is assumed by Quetelet in the 

 Bulletin de I'Academie Eoyale de Bruxelles, v. XIX, pt. I, p. 543. 



Babinet, a distinguished physicist, has proposed a method for determining 

 the heat required by plants for the performance of certain functions. He com- 

 pares the action of temperature to that of a force, such as weight, which pro 

 duces effects proportioned to the intensity of the cause and the square of th 

 time. He has not, however, made experience the basis of his hypothesis, and 

 it is rejected by Quetelet as unsound. According to the latter philosopher, by 

 the hypothesis of Babinet, if one day at 20° centigrade produces a certain 

 effect, two days having a mean of 10"^ centigrade should produce four times 

 10° or the effect of 40° centigrade, and four days at 5° centigrade should 

 exert an influence equal to sixteen times 5° or 80^ centigrade — results which 

 the general experience of horticulturists will not permit us to accept as true. 



Count Adrien de Gasparin, a minister of Agriculture and Commerce, and Peer 

 of France, who, by his numerous memoirs addressed to the societies of the de- 

 partments as well as to the Academy of Sciences, attained an honorable place 

 among contemporary agronomes, or scientific agriculturists, has also given 

 much attention to the question of the amount of heat demanded by plants.* In 

 his excellent Cours d'Agriculture, or Course of Agriculture, he suggests that 

 the mean heat of the day should be derived in part from the direct heat of the 

 sun, and not alone from that of the air, as is in general measured by meteorol- 

 ogists, because the motive power which induces the circulation of the sap is 

 the heat derived from the atmosphere and the soil in conjunction with the di- 

 rect rays of the sun. The rate of decomposition of the carbonic acid absorbed 

 from the air must be measured by the activity of the chemical rays of the sun, 

 and the growth of the plant is accelerated, we are aware, by exposure to its 

 full measure of sunshine. This method cannot, however, be readily verified in 



* Count Adrien de Gasparin was father of Count Agenor de Gasparin, whose virtues and 

 generons appreciation of the importance of the struggle that now rac-ks our nation have been 

 su fully exeui])litied in his enlightened labors in our behalf among his fellow-countrymen in 

 Europe. 



