STATE AGRICULTURAL SOCIETY. 393 



months, the temperature in the forests is considerably lower than outside 

 in the open country, there being at the same time a slow but steady out- 

 flow of air from the forest; and that during the night the temperature in 

 the forests is higher, while there is an inflow of air from the open country 

 into the forest. The mean annual temperature in the forest increases from 

 the surface of the ground to the tops of the trees (where it is observed to 

 approximate to what is observed in the open country) ; a result evidently 

 due to the facility of descent to the surface of the cold air produced by 

 terrestrial radiation, and to the obstruction offered by the trees to the solar 

 influence at the surface. 



The mean annual temperature of the woodland soil from the surface to 

 a depth of four feet is from 2 degrees to 3 degrees lower than that of the 

 open country. 



A series of observations was begun at Cornwath, Lanarkshire, in 1873, 

 at two stations, one outside the wood and the other inside the wood, in a 

 small grass plot of about fifty feet in diameter, clear of trees. From these 

 valuable results have been obtained relative to the differences in the daily 

 march of temperature, and the different rates of humidity, the most impor- 

 tant being the substantial agreement of the mean annual temperature of 

 the two places. The establishment of a station, with underground ther- 

 mometers, which it is proposed to erect under the shade of the trees close 

 to the station in the cleared space, will furnish data, which will not only 

 throw new light on the questions raised in this inquiry, but also on the 

 movements and viscosity of the air, and solar and terrestrial radiation. 



FORESTS AND LAKES A PROTECTION AGAINST FROSTS AND CHANGE- 

 ABLE WEATHER, AND OTHER IMPORTANT CLIMATIC MEMORANDA. 



Why forests and lakes protect the countries in which they are situated 

 from the extremes of heat and cold, and why the Swiss build their houses 

 on the sides of the hills and mountains instead of in the valleys, and also 

 shows the variability in the change of temperature caused by elevation. 

 This information is culled from the ninth edition of the " Encyclopedia 

 Britannica," and is as follows: 



Observations show that the rate at which the temperature falls with the 

 height is a very variable quantity — varying with latitude, situation, the 

 state of the air as regards moisture or dryness, and calm or windy weather, 

 and particularly with the hour of the day and the season of the year. In 

 reducing temperature observations for height, 1° for every three hundred 

 feet is generally adopted. In the present state of our knowledge this or any 

 other estimation is at best no more than a rough approximation, since the 

 law of decrease through its variations requires yet to be stated, being in 

 truth one of the most intricate and difficult problems of climatology await- 

 ing investigation at the hands of meteorologists. 



Among the most important climatic results to be determined in working 

 out this problem are the heights at which in different seasons the critical 

 mean temperatures, which have important relations to animal and vege- 

 table life, are met with in ascending from low lying plains in different 

 regions of the world. * * * Under this head by far the most important 

 class of conditions are those which result in extraordinary modifications, 



