B. TEURESTUIAL PHYSICS AND METEOROLOGY. 81 



(as some few of them do every season), it then returns north- 

 Avard or northwestward, and transports the sand which in the 

 desert formed a sand-storm to the southern coasts of Europe 

 as a sand-shower of oreater or.less duration. 



The satisfactory investigation of this subject is much im- 

 peded by the absence of barometric observations on the 

 southern shores of the Mediterranean ; and to remedy this 

 defect, M. Tarry has recently established new meteorological 

 stations at Mogadore, Morocco ; Terceira, Madeira ; and even 

 in the interior of the Sahara. 



IXFLUEXCE OF FORESTS ON THE TEMPERATURE OF THE 



GROUXD. 



The Bavarian jjhysicist Ebermayer has investigated the in- 

 fluence of forests on the climate of the neio-hborhood as 

 shown by the numerous observations recorded in that king- 

 dom. Amonoj his conclusions are the following: results as to 

 the temperature of the ground, as determined by thermome- 

 ters sunk to depths of one and six inches, and of one, two, 

 three, and four feet. For the upper layer of earth, within 

 one foot of the surface, the minimum monthly iean temper- 

 atures occur both in open and in wooded regions in the month 

 of January ; only on the high mountains does the lowest 

 temperature occur in February. The temperature increases 

 from February on, until its maximum in July ; at the liigh 

 stations only does the maximum occur in August. From 

 July or August the temperature decreases to January or Feb- 

 ruary. To the agricultural interests it is especially impor- 

 tant to note that the monthly increase of temperature is most 

 rapid in May, and is nearly as great in April ; it is least in 

 June and July. Concerning the strata lower than one foot, 

 Ebermayer finds that the monthly increase in temperature is 

 greater in June and July than it is in the upper stratum. 

 The loss of temperature is, in the upper stratum, most rapid 

 in November and October, and least in the coldest weather 

 in January and February. In forest-covered places, the low- 

 est temperature occurs in February, and continues to June, 

 during which interval the ground is cooler than the air; in 

 July and August the ground is somewhat warmer than the 

 air. The greatest difference between the temperature of free 

 and forest land occurs in May, and the least in June. The 



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