142 Marcet on Nocturnal Radiation. 



nected by closely interwoven and matted radicles, in colour 

 approaching to a cinnamon brown. 



We give an illustration of the natural size of this moss, and 

 also of .its various parts magnified. It fruits throughout 

 August and September. 



MARCET ON NOCTURNAL RADIATION. 



Professor Marcet communicated to the Societe de Physique et 

 (VHistoire Naturel the following paper on " The Effects of 

 Nocturnal Radiation in Tropical Regions." We translate it 

 from the Archives des Sciences : — 



"I profited/' says the professor, "by the prolonged 

 sojourn of one of my sons in Australia, to engage him in 

 certain observations on the effects of nocturnal radiation in a 

 climate so different from our own. With this end in view, I 

 supplied him with the necessary directions, and with thermo- 

 meters on whose accuracy I could rely. 



" Observations made during several years back at Geneva 

 and Montpellier leave no doubt that in temperate climates, 

 at the moment of sunset, provided the sky be clear, the 

 temperature of the air in immediate contact with the soil is 

 notably lower than the temperature of the same air at an ele- 

 vation of a few feet. Although, so far as I am aware, 

 observations had not been made in the region of the torrid 

 /one, it appeared natural to conclude, d priori, that they would 

 exhibit the same phenomena, with perhaps greater intensity, 

 on account of the great transparency of the air, which is 

 favourable to radiation; and because in those countries the 

 surface of the earth is more strongly heated during tho day, 

 and might be expected to radiate with corresponding vigour 

 during the night. I learnt, not without surprise, that this was 

 not the case. It appeared, in fact, to result from a series of 

 observations made by my son at his station on Logan Downs, 

 in Queensland, 22° south latitude, and thirty or forty leagues 

 distant from the sea, that the phenomenon of increase of tem- 

 perature, in proportion to elevation above the soil, was not 

 observed either at sunrise or sunset, or if it exists at all it is to 

 an extent scarcely perceptible, lie found, for example, by a 



Lea of obeervationi made in March and April, 1802, under 

 circumstances that were apparently very favourable to nocturnal 

 diation, that the difference between a thermometer placed at 

 three centimeters above the ground, and another at a meter 

 and .'i- half above it, did not usually exceed from 0°,l to 0°,2 Cent., 

 three times it was from to •'!, and once from to 4. 



"This n suit, completely unexpected by me, could not bo 



