the Roccella tinctoria and Evernia Prunastri. 251 

 Lecanoric aether: — 



JEther from alpha-orsellic acid (orsellesic aether of Sten- 

 house) : — 



I. II. 



Carbon . . 61*24 61*13 



Hydrogen . 6*26 6*15 



Oxygen . 32*50 32*72 



iEther from beta-orsellic acid (Stenhouse) : — 



I. II. III. 



Carbon . . 60*82 60*75 60*83 



Hydrogen . 6*27 6*15 6*27 



Oxygen . . 32*91 33*10 83*00 



On comparing the preceding analyses with one another, 

 any one conversant with organic chemistry will immediately 

 perceive that the differences are not greater than those usually 

 found in analysing the same substance from different sources. 

 The properties of these aethers are also identical as far as they 

 are known. I found lecanoric aether to have exactly the same 

 properties as those ascribed to pseudo-erythrine by Heeren 

 and Kane. I was also unable to discover any characteristic 

 difference between lecanoric aether and the aether from erythric 

 acid. Mr. Stenhouse says of orsellesic aether, " This aether 

 cannot be distinguished in its external properties from the 

 lecanoric and erythric aethers;" and the aether from beta- 

 orsellic acid, according to him, "cannot be distinguished in 

 appearance from the orsellesic, lecanoric or erythric aethers, 

 with which bodies in its properties and reactions it very closely 

 corresponds." I therefore maintain that all these aethers are 

 nothing more nor less than lecanoric aether. Now lecanoric 

 aether consists of C 18 H 8 8 + C 4 ¥1^0=0^ H J3 9 , and its 

 calculated composition is as follows : — 



S2 



