TMK CLIMATh: Ol' L()URENi;0 MARQUES. 3I9 



until it reaches the minimum, and rises again to a second maxi- 

 mum in Autumn. I possess complete observations only for the 

 year 1912. In these observations (see Table No. XVI j I notice 

 two maxima, one in February and the other in September, re- 

 sjjectively 45.6 and 44.7 uctinometric degrees, corresponding to 

 the two maxima of the other hemisphere ; the minima are 36.3 

 and 41.2 actinometric degrees in May and December respectively. 



The observations are made at IX, XII, and XV, which does 

 not suffice to permit of the study of the double daily variation : 

 in these observations a higher value is recorded, first at noon and 

 then in those taken at IX. 



These observations, such as they are, may Ije of interest to 

 agriculturists. 



For the study of solar radiation, l)esi(les the actinometer, the 

 Observatory employs a thermometer of maximum solar radiation, 

 with a blackened bulb enclosed in a vacuum glass sheath, and a 

 thermometer of minimum nocturnal radiation containing alcohol, 

 which is placed in such a way that the bulb remains on the focus 

 of a parabolic metallic mirror, turned towards the zenith. 



The figures presented in Table No. X\T, being the average 

 for three years, show only the annual variation accompanying 

 that of the temperature in the shade. 



The respective diagrams refer to the maximum means of 

 solar radiation and to the absolute minimum of nocturnal radia- 

 tion in each month. 



The absolute maxima and nu'nima of three years in these 

 two thermometers are 75.6° C ( i08.i° F) and 7.8° C (4>'>"Fj. . 



Grass Thermometers. 



Temperatures over the grass are observed with two kinds of 

 thermometers, one of maximum with blackened bulb and another 

 of minimum, for the j)urpose of getting an approximate idea of 

 the greatest quantity of heat received and radiated by the plants. 

 Their records, averaged for three years, shewn in Table No. 

 XVII, are of special interest to agriculturists, and noticeably 

 follow the annual march of the temperature : The extremes re- 

 corded during the same period are ^2.2° C (129.6° F) and 

 5.7° C (42.3- F). 



Temperature of the Earth. 



The temperature of the earth affords consideral)le interest 

 on account of" its effects on the temperature of the air, principally 

 in respect of the latter's variations. 



The soil warms up and cools down the greater its conducti- 

 bility, radiating power, absorbing power, and calorific capacity, 

 in sandy soil all these favourable circumstances occur to the 

 greatest extent, while the opposite is the case with water. 



The temperature of the soil, though less important to veget- 

 able life than the temperature of the air, is nevertheless an 



