1818.] Account of a Mission to Ashantee. 9 



8. One volume of pure phosphuretted hydrogen mixed with 

 from two to five volumes of* pure nitrous gas aftbrd a most bril- 

 liant explosion by one or more electric sparks, as was discovered 

 by Dr. Thomson. When duly proportioned (I find 1 to 3j-, and 

 not 1 to 3, as Dr. Thomson), the result is phosphoric acid and 

 water, with azotic gas two or three per cent, less than i the 

 volume of nitrous gas. When more or less than 3i of nitrous 

 gas is vised, the residue of gas after the explosion contains 

 oxygen gas or hydrogen gas accordingly ; rarely any phosphu- 

 retted hydrogen. Dr. T. says that no alteration is produced by 

 mixing nitrous gas and phosphuretted hydrogen. This is correct 

 if we are to understand immediately ; but not otherwise : for, by 

 standing one, two, or three hours, the whole phosphuretted 

 hydrogen is consumed (if the nitrous gas be in excess), and 

 there is left a mixture of nitrous gas, nitrous oxide and azotic 

 gases, amounting to about half the volume of the original mix- 

 ture. Dr. T. found that a bubble of oxygen causes a mixture of 

 nitrous and phosphuretted hydrogen to explode ; by analogy I 

 concluded that a mixture of phosphuretted hydrogen and oxygen 

 would explode by a bubble of nitrous gas, and found it accord- 

 ingly. 



9. Nitrous oxide and phosphuretted hydrogen explode by a. 

 spark, but undergo no change by simple mixture for several 

 hours at least. The due proportions are nearly three to one. 



Experiments on phosphuretted hydrogen are most likely soon 

 to determine the controverted question respecting the constitu- 

 tion of phosphoric acid, as well as those concerning the quan- 

 tities of azote and oxygen in the nitrous compounds. 



I remain yours, 



John Dalton. 



Article III. 



Some Account of a late Mission to Ashantee, 



In the " Voyage du Chevalier Des Marchais," published in 

 1730, by Le Pere Labat, is a map of Guinea drawn by Dan- 

 ville. In this map, between 30 and 40 G. miles north of Cape 

 Coast Castle, is represented the southern frontier of the kingdom 

 of Asiante. Its breadth from west to east is between 50 and 60 

 miles: its northern frontier is not denned. M. Des Marchais 

 makes no mention of this country in his travels (which indeed 

 were confined to the eastern districts of Guinea) ; but in the map 

 it is called Royaume ties puissant, and is divided into seven 

 provinces. 



During the last 80 or 90 years the Ashautees appear to have 



