26 



Magnesia, 16.54 



Phosphoric acid, 83.46 



100.00 

 It contained no watei", and must therefore be composed according to 

 the formula, 2 M^O-f-S Pj^j- ^^^^^ formula, the author shewed, 

 could not be reconciled with the prevalent views of the constitution 

 of phosphates, and the existence of this salt aught tiiei'efore lead to 

 some modification of these views. 



The following Donations were presented : — 



The Journal of the Royal Agricultural Society of England. Vol V. 

 Part 2, — By the Society. 



Transactions of the Society for the Encouragement of Arts, Manu- 

 factures, and Commerce. Vol. LV. — By the Society. 



Memoirs and Proceedings of the Chemical Society. Part 11. — By 

 the Society,, 



The Journal of Agriculture, and the Transactions of the Highland 

 and Agricultural Society of Scotland, for March 1845. — By 

 the Society. 



Fifteenth Report of the Scarborough Philosophical Society, for the 

 year 1844. — By the Society. 



Monday, 17th March 1845. 

 Sir GEORGE S. MACKENZIE Bart, in the Chair. 



The following Commmunications were read : — 



1. On the Improvement of Navigation in Tidal Rivers. By 

 David Stevenson, Esq. 



Three compartments are pointed out as existing in all rivers, when 

 viewed in connection with the sea, possessing different characteristics, 

 and i-equiring different classes of works for their improvement. 

 These are, Jlrst, The " sea proper," characterised by the presence 

 of unimpaired tidal phenomena, and including all works connected 

 with the improvement of bars. Second, The " tidal compartment 

 of the river," characterised by the modified flow of the tide, produced 

 by the inclination of the bed, and embracing works connected with 

 the straightening, widening, or deepening, of the beds of rivers ; the 



