102 DE8CRIPTI0N OF THE FIRS. 



which he has inferred, that the opinion I had advanced 

 witli regard to the nature of potassium is unfounded. He 

 will have observed, that, in my second paper, published in 

 the supplement to your last volume, which accompanied 

 that number, 1 have taken notice of the greater number of 

 these facts; and, that 1 had given them due consideration 

 both in conducting the additional experiments of which I 

 have given an account, and in forming the conclusions I 

 had drawn. It is therefore unnecessary for me to make any 

 observations on his statements in their present form. The 

 whole subject, from the difficulties which attend it, 1 consi- 

 der as c>pen to farther investigation, though I may add, that, 

 without placing any undue confidence in my own experi- 

 ments, I do not consider their results as invalidated ; and, 

 that I still regard the view 1 have given of the nature of the 

 metalloids as the one which is most probable, nor shall I 

 have any hesitation in engaging in the more minute discus- 

 sion of the groi^nds on which it rests. 



VII. 



Description of Firs, illustrated hy Dissections* By Mrs* 

 Agnes Ibbetson. 



To Mr. NICHOLSON. 

 SIR, 



AranrremeTit A AM now to give a description of the fir tribe of plants, 

 of the fir tribe, seldom, 1 believe, studied, 4hough well worthy of attention, 

 as differing more in many important particulars than any 

 natural order of plants I am acquainted with. Though sel- 

 dom interfering in the arrangements of botany, I have ven- 

 tured to place the thujas with the cypresses, allotting the 

 cedars to the genera they appear to belong to. For they 

 haye been hitherto placed without the least regard to their 

 flower or fruit; else could the white cedar be called a cedar, 

 or the balm of gilead fir a pine? I shall divide them into 

 three sorts, the pine, the cypress, and the cedar, placing 

 the various apecies according to their fructification. 



Firs 



