INTRODUCTION TO THE FLORA. 237 



considering. In giving them it is hardly necessary to say that 

 they are a mere essay, of course as true and thorough as I can 

 make it at this present time, but still, that with regard to various 

 points which come within their range, our information and 

 observations are very limited and incomplete. 



1. In the shade, as compared with the temperature of the air 

 at four feet from the ground, mean temperature is lower upwards, 

 and several degrees lower upon the grass. The daily maxima in 

 the sun are higher than the daily maxima in the shade, on an 

 average of from 5 to 6 degrees in Winter to from 20 to 30 

 degrees in Summer. 



2. At a depth of one foot in the ground the mean temperature 

 is on the average fully one degree above the mean temperature 

 of the air in the shade, the ground being proportionately or 

 absolutely lower than the air in Spring and Summer, higher in 

 Autumn and Winter ; and the difference between the extreme 

 months of the year being less in the ground than in the air by 5 

 degrees. 



3. As we ascend from the low country amongst the hills, the 

 mean temperature of the air sinks at an average rate of about 

 one degree Fahrenheit per hundred yards, the lowering being 

 apparently more in maxima than in minima, above the average 

 in Spring and Summer, below it in Autumn and Winter, and the 

 ground temperatures, especially the minima, falling less rapidly 

 than the aerial means. 



4. The di.stribution of absolute winter minima follows a 

 totally different plan from that of the sums of summer heat ; 

 whereas these latter fall gradually as we ascend the hills, winter 

 minima, on the contrary, are often conspicuously less extreme at 

 an elevation than in the open low country, and instead of the 

 temperature growing gradually lower as we ascend, within certain 

 not very narrow limits it rises. 



5. As compared with the inland low country, at the sea-side 

 the annual means arc slightly higher, and the absolute winter 



July 1889. 



