AUSTEALIAN NIGHT TEMPERATURE. 



617 



Mitchell made no hygrometrioal obgervations in June and July, and 

 only four in May, yet there ia other evidence to show that the dryness 

 cannot always have been remarkable.- In May the hygrometer indi- 

 cated '764, '703, "934, or nearly saturation, and "596 ; yet the sunrise 

 temperature was on those occasions 25°, 28°, 30°, and 34°. On the 

 22nd of May the Grass was white with hoar frost, and the thermometer 

 was at sunrise 20° under canvas and 12° in the open air. On the 5th 

 of July, when it rained all day and the tents were ' frozen into boards,' 

 the thermometer sank during the night from 38° to 16°. No doubt this 

 power of resisting cold is connected with the very high temperature to 

 which Australian vegetation is exposed at certain seasons, and this is 

 horticulturaUy a most important consideration. We find that in 

 latitude 32° 8. in January (our July) the thermometer stood eight days 

 successively above 100°, and even reached 115° at noon; that it was 

 even as high as 112° at 4 p.m. ; that in the latter part of February one 

 degree nearer the line it was twice 105° and once 110° ; that in March, 

 one degree further northward, it frequently exceeded 100°, and there 

 was not much fall in this excessive temperature up to the end of April. 

 This will be more evident from the following 



Table of Noon-day Temperatures. 



" Even such heats as these do not, however, destroy the power of vege- 

 tation, for we find in the midst of them all sorts of trees in blossom ; a 

 few bulbs, and even here and there (ia damp places, no doubt) such soft 

 herbs as Q-oodenias, Triohitiiums, Heliohrysuin, Didiscus, Teucrimn, 

 Justioia, herbaceous Jasmines, Tobacco, and Amaranths. During these 

 heats the night temperature seldom remains high. Sometimes, indeed, 

 the thermometer was observed as much as 88°, and once even 97° at 

 sunrise, the average noon-heat of the month being 97^°, but generally 

 the temperature is lower. Thus ; 



Nov. and Dec, averaging 102° at noon, 62' 



Jan. and Feb. „ 97| „ 61 



Feb. and March „ 90 „ 61 



March ... „ 95 ,,'68 



. Temperature 

 occasioiially at Sunrise. 

 , 58°, 61°. 



60 59 47°, &o. 



59 64 48 &c. 



65 51 47 &o." 



These facts seem to demonstrate that it is the purpose of 

 nature to reduce the force which operates upon the excitability 



