Baron L. Von Buch an the Temperature of Springs. 169 



ourselves that it arises from no other cause than that which 

 warms the rock and soil of the north. 



From Southern Europe to the Tropic there is but onp rainy 

 season, which continues from November until April. In this 

 great tract, no rain falls from the month of May onwards. 

 Hence, as little of the summer heat will be distributed through 

 the soil, and subjacent rock, by means of percolating water, as 

 of the winter's cold in frozen districts. It is only that tempera- 

 ture, which the rain already meets with at the period of its fall, 

 which it carries along with it to the interior, and the springs 

 issue forth with this temperature. Hence the heat of the 

 springs at Orotava is probably the mean of the months of Fe- 

 bruary and March. 



From observations on springs in Grand Canary, it results, 

 that the temperature of the rock or soil for the northern decli- 

 vity of the island is about 13|° R., while the mean of the atmo- 

 sphere is 18° R. These, and other similar facts, mentioned by 

 Von Buch, seem to warrant the conclusions, that the tem- 

 perature of springs in northern regions, where the Surface wa- 

 ter is frozen, is higher than the mean temperature of the super- 

 incumbent atmosphere; that in temperate regions, where the 

 surface, and consequently the percolating water, is not fro- 

 zen, the temperature of springs is that of the mean of the at- 

 mosphere ; 3. and lastli/, that, in the countries from the south of 

 Europe to the Tropic, the temperature of springs is lower than 

 that of the medium temperature of the atmosphere. 



Account of a New Method of Filtering Water^ invented by 

 James White, Esq. Engineer, 



JL HE filtration of water in a mountainous country like Scot- 

 land, where water is in general pure, is comparatively a sub- 

 ject of less interest than in flat and fenny districts, or in great 

 cities like London, which is supplied chiefly from the collected 

 waters of the Thames. The means of purifying water under 

 such circumstances, is a matter of the first importance to the 

 health and comfort of the community. 



