TEMPERATURE DIFFERENC'E.S IN GLADES AND PLAINS. 



87 



The third figure enables us to compare th<^ dKIereuces between glade 

 and pliiiii. They are small, but eurious. Tlie line tor minima (dotted 

 line) and for maxinni (broken line) hav(^ changed ithu-es. Tlie maxima 

 are reduced generally, though slightly, in glades as compared with 

 plain, but the minima are exaggerated by a quantity two or three times 

 as large. The result is that the glade is cooler in mean temperature 

 for three of the seasons, and that its diurnal ami»l.itude is sharpened 

 or its climate made more rigorous. Tn winter the advantages are with 

 the glade, in the other seasons against it. 



To bring- out more clearly the advantage in range possessed by the 

 plain over the glade. Fig-. 47 has been constructed. The distance from 



Fio. 47.— Amplitude of W—G (lower curve) and W— O (upper curve), Swedish observations. 



the zero line to the first curve gives the reduction of daily ami)litude 

 in woods as compared with plains, to the second of woods as compared 

 with glades. The distance between the lines is the difference in ampli- 

 tude favorable to the plain as compared with the glade. It does not 

 change sign during- the year, and glade and plain are alike for only one 

 month, that of July. Fig. 48 gives the temperature values of TT— 6^ 



_ W-G 

 Fig. 48. — Dil'enMice ol' snil tiiniicniturc at 211 feet in depth. 



W-P 



(nnbr(»ken line) and IT— /' (hrokcn line) lor the soil at the depth of 

 liO inches. As is to be expected, the temperature of the glade soil is 

 intermediate between that of the woods and that of the jdain. 



Dr. Ilamberg- also studied the ettect of clear and (doudy weather on 

 the differences between glade and i)lain. The following- table gives 

 tlu'inean values oC (i —V foi- cleai- and cloudy weather at the three 

 honrs (»f daily obseivation. The clonds cause the temi)eratures at the 

 two stations to ajjjjroach th(^ same degree, reducing' ii — V to zero: 



