220 THE ]S"ATUBAL HISTORY BEYIEW, 



The author refutes tlie theory of M. Taupenot, that these tufas 

 were deposited at the bottom of an ancient lake, and concludes that 

 they were formed by running waters, issuing from numerous springs^ 

 charged Avith calcareous matter which formerly rose in the valley, 

 and gradually encrusting the mosses, leaves, or other fragments which 

 grew or became arrested in their course. The arguments in support 

 of this hypothesis are given with considerable detail and clearness. 

 From the various forms and stratifications observed he traces the 

 origin and course of the principal streams ; and he exemplifies his 

 views by the encrustations now taking place in the park of Castries, 

 along the channel and aqueduct conveying the water of a neigh- 

 bouring spring to the chateau, and which supply him amongst 

 others with two remarkable facts : that these encrustations have taken 

 place along the steps of a cascade to the extent of sixty centimetres 

 (nearly two feet) in eight years ; and that the more rapid is the 

 current the greater is the deposit. In point of time, he considers 

 the relation of these deposits to the quaternary period as exceedingly 

 obscure, but believes them to be much more recent than has been 

 generally supposed. 



Dr. Planchon's determinations of the species found are amongst 

 the most satisfactory we are acquainted with. He has more or less 

 certainly established the presence of the following thirty species, or 

 marked varieties. 



Clematis vitalba, L Laurus nobilis, L. 



Acer m.onspessulanum, L. Buxus sempervirens, L. 



opulifolium, L. Ficus carica, L. 



var. neapolitanum Alnus campestris, L. 



Yitis vinifera, L. Quercus sessiliflora, 8m. (Q. ro- 



Kubus discolor, Weihe (E. fruti- bur, L.) 



cosus, L.) ilex, L. 



Cotoneaster pyracantha, Pers. Salix cinerea, L. 



Hedera helix, L. Alnus glutinosus, Linn. 



Cornus sanguinea, L, Pinus Laricio Poir ? (or var. 



Viburnum tinus, L. Salzmanni ?) 



Rubia peregrina, X. var. angus- Smilax aspera, L. 



tifolia Typha angustifolia, L. 



Praxinus excelsior, i. Sparganium ramosum, L. 



ornus, L, Pteris aquilina, L. 



Phillyrea media, L. Scolopendrium officinale, Sj7i. 

 angustifolia, L. Marchantia conica, L. 



