190 0)! (he Causes which have operated 



as to require for its exhibition nuich more delicate hygro- 

 metrical tests. 



The facts acl\Mnced in this lecture, afl'urd no new argn- 

 menis in favour of an idea to which I referred in my last 

 commiuiieation to the Society, that of hydrogen bcine ^ 

 comnKVii principle in all inilHi^iinable bodies; antl excein in 

 instances which arc sliil ui.der invesiigation, and concern- 

 ing which no precise conckisions can as yet be drawn, the 

 generalization of Lavoisier happily applies to the explana- 

 tion of all the new phosnoniena. 



In proportion as progress is made towards the knowledge 

 of pure combustible bases, so in proportion is the number 

 of n)etal!ic substances increased ; and it is probable that 

 sulphur and phosphorus, could tbcy be perfectly deprived 

 of oxygen, would belong to this class of bodies. Possibly 

 their pure elementary matter may l^e procured by distilla- 

 tion, at a high heat, from metallic alloys, in which they 

 have been acted upon by sodium or potassium. I hope soon 

 to be able to try tliis experiment. 



As our inquiries at present stand, the great general di- 

 vision of natural bodies is into matter wliicli is, or may be 

 supposed to be, metallic, and oxygen ; I ut till the problem 

 eoncernin?! the nature of nitrogen is fully solved, all syste- 

 matic arrangements made upon this idea must be regarded 

 as premature. 



Explanation of the Figures. 



Fiff, 1. The retort of plate, glass for heating potassium 

 in siases. 



Fio:. 'i. The tra.v of platina for receiving the potassiu-n. 



Fig. 3. The platina tube for receiving the t:av in experi- 

 ments of dislillaiion. 



Fiy;. 4. The apparntus for taking the Voltaic spark in 

 sulpf)ur and phosphorus. 



XXVIT. On the Causes which have dperaied in Vie Prnrluc- 

 iion of Valleys. Bi/ John Caur, Esq., of Manchester. 

 >-No. III. 



To Mr. Tilloch. 



Sir, i-T was not my intention to have intruded again into 

 vour verv respectable journal, vvhereili, indeed, I tirst inci- 

 dentally appeared, solely with a view of showing, in opj\o- 

 sition to some hvpothetical notions, that mouinf; water has 

 been, and yet continues to be, the great and general agent 



of 



