132 On a New Species of Manna 



tions usually employed, — a matter of interest when we consider the 

 phosphate of lime required for certain plants, — we sliould recollect 

 that when free carbonic acid is present in water, the phosphate, like 

 carbonate of lime, though not to the same amount, is very soluble. 

 Hence, especially when, as noticed by Mr Austen, phosphate of lime 

 is disseminated in the state of fresh corprolites amid detrital matter, 

 and water containing free carbonic acid is present and can have ac- 

 cess to it, the phosphate of lime would be in a condition to be re- 

 moved and disseminated. Mr Austen has alluded to the mixture of 

 such bodies with vegetable matter, to the decomposition of which, 

 with animal matter also, we might look for some, at least, of the car- 

 bonic acid that would aid the solution of the phosphate of lime. As in 

 the case of the carbonate of lime previously noticed, when the solution 

 of this phosphate met with the silicates of potash or soda, whilst per- 

 colating amid the rocks, the silicates would be decomposed by the car- 

 bonic acid, and the phosphate of lime thrown down. We should ex- 

 pect, — in the same manner as carbonate of lime often replaces the 

 original matter of a shell which has been decomposed and removed 

 from the body of a rock, leaving those cavities commonly termed 

 casts, — that phosphate of lime, in localities where, from accidental 

 circumstances, it was somewhat abundantly filtering through rocks, 

 would also enter these and any other cavities, filling them under the 

 needful conditions of deposit. In like manner as we find carbonate 

 of lime separating itself from mud and silt in which it was dissemi- 

 nated, forming the nodules so common in calcareo-argillaceous depo- 

 sits, should we also expect disseminated phosphates of lime to do the 

 same under fitting conditions ; so that it would not necessarily fol- 

 low, however true in numerous cases, that nodules containing much 

 phosphate of lime were coprolitic. We can readily imagine circum- 

 stances very favourable for the solution and spread of these phos- 

 phates amid layers of mud and silt. We find such phosphates sur- 

 rounding some fossils, such as crustaceans from the London clay, 

 leading us to infer a connection between the animal matter and this 

 substance. 



On a New Species of Manna from New South Wales. By 

 Thomas Anderson, M.D., F.R.S.E., Lecturer on Chemis- 

 try, and Chemist to the Highland and Agricultural Society 

 of Scotland. Communicated by the Author. 



The saccharine exudations of plants which have been classed 

 under the generic term of Mannas, present, in all instances, 

 a close resemblance in their chemical constitution. Their 



