Mr Murray on the Physwhg}) of ‘the Root in Plants. 531 
and vegetable kingdom ; and rather the more am I convinced that 
neither of them can say to the other, I have no need of thee.” 
The experiments of Priestley, Saussure, Sennebier, and In- 
genhousz, are very clear and explicit ; and even Sir Humphry 
Davy has set his seal to the doctrine. ^ But in all these, and 
others of more modern date, aquatic plants^ though by my ex- 
periments they seem chiefly concerned in the renovation of the 
atmospherej appear to have been too little heeded. ’ 
The Conferva bullosa receives its specific name from its copi- 
ous disengagement of oxygenous air-bells. The Epilohium ij 
also remarkable in this way ; but I know not if I have seen any 
to compete in that respect with the Potamogeton verticillatum. 
It is in this last copious and uniform. 
M. Guy Lussac has found that the air in water contains 62 
per cent, oxygen, whereas that of our atmosphere exhibits only 
21. This is a very important circumstance, and must not be 
forgotten. 
It is admitted that plants as well as animals do, at nighty 
evolve carbonic acid gas; but the noxious gas at this period 
cannot mingle, in either case, with the atmosphere to disturb its 
salubrity. The gas falls by its own weight, being now chilled, 
and is finally absorbed by the earth. This check is only requir- 
ed during the day^ and here vegetation ministers its ample 
counterpart. 
Vegetation, then, is the grand oxygenemetron (if I may be 
allowed to coin a word for the occasion) j by which the purity of 
the atmosphere is preserved inviolate, amid the vicissitude of 
clime and season. The Great Geometer of the Universe clothed 
the lilies of the field,” before other animated forms of being took 
the stations assigned them, in his magnificent and beautiful 
creation. 
Art. XXII.— of a Whirlwind at Roseneath in Dun-, 
hartonshire. By J ames Smith, Esq. of Jordanhill, 
F. R. S. E. In a Letter to Dr Brewster. 
My dear Sir, 
On the 18th ult. a whirlwind of considerable violence took 
place here ; but, fortunately, without doing any material da- 
