M. Marchand on Natural fTaters. 307 



that the collective names of the rocks in the tabular sections are 

 correct, both on grounds of principle and of geographical propriety. 

 The tabular section of Wales here given differs not at all from a 

 general section exhibited by him in 1833. 



On the Physical and Chemical Constitution of Natural Waters. 

 By M. E. Marchand. 



From the researches which 1 have now for a long period 

 made upon the physical and chemical constitution of natural 

 waters, and their geological origin, the following conclusions 

 may be drawn : — 



1^^, All natural waters, at least in the circumstances of 

 which I shall presently speak, contain iodine and bromine. 



2d, All these waters contain lithia. 



3i/, The whole of them, when they take their origin from su- 

 perficial deposits connected with chalk, or in calcareous dis- 

 tricts, contain iron. 



4M, The origin of iodine and of bromine in water proceeds 

 from the transportation of these principles from the water of 

 the sea, from the vapours or the aqueous particles which in- 

 cessantly escape from it, and which, transported to the con- 

 tinents, fall to the earth, in the state of rain, of snow, or of 

 hail. The waters composing rain and snow generally contain 

 an appreciable proportion of iodurets and of bromurets. 



bth, In well-wooded countries, iodine and bromine may 

 disappear from the water which holds them in solution, by 

 passing to a saline state under the influence of vital forces, 

 due to the number of mineral principles engendered by vege- 

 tation. The ashes of the greater part of our forest trees, 

 elm, beech, fir, &c., contain iodine. 



%th, The determinating causes of goitre and cretinism are 

 not to be found in the existence of carbonate of magnesia in 

 the waters which those afflicted with goitre and cretinism 

 «se for their necessary food. 



1th, The determinating cause of these maladies exists 

 rather in the absence of iodine and bromine from the number 

 )f constitutive principles of these waters. 



8M, The physical and chemical constitution of water varies 

 sach day in the year, and, perhaps, even in every moment irf 

 he day. At the seasons when the temperature is highest, the 



u2 



