260 



METEOROLOGICAL OBSERVATIONS AT C'ARXWATH. 



In the last column of Table II. are given the differences between 

 the various temperatures observed at the exposed and shaded sta- 

 tions respectively, the sign "minus" indicating that the temperature 

 at the shaded station was the lower of the two, and the sign " plus," 

 that it was the higher. The most important of these results are 

 those which refer to the mean temperatures of the soil, from which 

 it appears that the soil under shade was for the period l°-9 colder 

 than that fully exposed to the rays of the sun at a depth of 3 

 inches, 2 0, 1 at 12 inches, and 2 o, at 22 inches. The differences 

 for each of the months are as follows : 



It is evident from the figures for the different months that 

 caution is necessary in deducing any general conclusions from the 

 results obtained during such veiy exceptional weather as prevailed 

 from March to July 1877, which, for the earlier portion of the 

 period, had a temperature much under the average, and was chai'- 

 acterised throughout by a great want of sunshine. This, however, 

 is plain, that soil, closely shaded by trees from the sun, has a 

 temperature greatly lower than soil exposed to the sun ; and 

 looking at the results in the light of the observations now being 

 made at Forest Stations in Germany, the deficiency in the tempera- 

 ture of the soil shaded by trees is greatest in the summer months. 

 During July 1877 we have seen that the temperature of the soil 

 in shade was about 4 O- lower than that of the soil exposed to the 

 sun, the distance between the two places where this great difference 

 obtained being only 30 yards. Particular attention will be paid 

 to this point in the discussion of next year's observations, together 

 with the influence of extreme temperatures, great changes of tem- 

 perature, and changes of weather from clear to clouded, wet to 

 dry, and vice versd. The whole question with regard to the lower- 

 ing of the underground temperature, according to the degree in 

 which it may be screened from the sun's rays, is a vital one as 

 affecting certain departments of practical arboriculture, such as the 

 thinning trees, as was pointed out by Mr M'Corquodale at the 

 meeting. In all probability this lowering of the temperature of 

 soil shaded by trees extends as far clown at least as the roots 



