392 Scientific IntelUgence. — Natural Philosophy. 



pulsions in cases where not only the distances, but the quantities 

 of heat are different. The above principle of the repulsions be- 

 ing inversely as the square of the distance, might easily be shewn 

 to accord with the law of temperature and the law of Boyle. 

 Any variation in the quantity of heat, will, ccet. par., produce 

 proportional variations in the logarithms of the repulsions. Per-^ 

 haps the same property belongs to magnetism or electricity, if 

 not to gravitation itself. Henry Meikle. 



2. The Beech-Tree a Nonconductor of Lightning. — Dr 

 Beeton, in a letter to Dr Mitchill of New York, dated 19th 

 July 1824, states, that the beech-tree (that is, the broad-leaved 

 or American variety of Fagus sylvaticd) is never known to be 

 assailed by atmospheric electricity. So notorious, he says, i» 

 this fact, that, in Tenessee, it is considered almost an impossi- 

 bility to be struck by lightning, if protection be sought under 

 the branches of a beech-tree. Whenever the sky puts on a threat- 

 ening aspect, and the thunder begins to roll, the Indians leave 

 their pursuit, and betake themselves to the shelter of the nearest 

 beech-tree, till the storm pass over ; observation having taught 

 these sagacious children of nature, that, while other trees are 

 often shivered to splinters, the electric fluid is not attracted bv 

 the beech. Should further observation establish the fact of the 

 nonconducting quality of the American beech, great advantage 

 may evidently be derived from planting hedge-rows^ of such 

 trees around the extensive barn-yards in which cattle are kept, 

 and also in disposing groups and single trees in ornamental 

 plantations in the neighbourhood of the dwelling-houses of the 

 owners. 



HYDROGRAPHY. 



3. Silica in Springs is dissolved by means of' Carbonic Acid, 

 — Dr Karsten remarks, that, if so feeble an acid as the acetous, 

 is capable of dissolving silica, it is not improbable that the car- 

 bonic acid may have the same property. This conjecture he has 

 confirmed by experiment. The experiment may be made as 

 follows. Decompose a portion of liquor silicum by means of a 

 superabundance of any acid, the muriatic, for example, and 

 neutralize the clear fluid with carbonate of ammonia, at the 

 lowest possible temperature. The carbonic acid evolved by this 



