319 



and any resemblance as indicated by the eye, between selected 

 pieces of this and true Verd Antique marble, affords no ground 

 for argument in relation to the name, while the general physical 

 characters and chemical composition show it to be entirely dif- 

 ferent from any marble, scientifically considered. But this beau- 

 tiful mineral has been introduced as an ornamental stone, capable 

 of resisting the destructive effects of our climate, and it is there- 

 fore in its economical and technical relations that its highest 

 value consists. " Verd Antique Marble," as is well known, 

 becomes changed after an exposure of twelve months to the air 

 and storms ; and to class an enduring Serpentine with so perish- 

 able a rock, would be doing injustice to the enterprise to which 

 we are indebted for its ornamental uses. 



In regard to chemical analyses of such compound rocks, no 

 trustworthy results can be obtained by decomposing them and 

 separating the earths singly, and then, by a reconstruction of 

 compounds, assuming a composition. It is only by a kind of 

 proximate analysis, in which each carbonate, hydrate and silicate 

 is separated from the others present, that we get a truthful and 

 clear view of the composition. By this mode of analysis, the 

 Serpentine of Reading, or Proctorsville, Vermont, proves to be 

 Serpentine, consolidated and variegated by anhydrous carbonate 

 of magnesia ; while the Lynnfield mineral, is a magnesian rock 

 and slate containing carbonate of magnesia also. 



Prof. William B. Rogers referred briefly to observations 

 recently made by him, and still in progress, on the varia- 

 tions of Ozone in the atmosphere. 



In making these observations, he uses the prepared paper and 

 scale of colors of Schonbein's Ozonometer, which, although 

 imperfect as a means of comparison, is the best for practical use 

 yet devised. The slip of paper is suspended out of doors in a 

 box open only at the bottom, so as to be shielded from the rain 

 and snow, and from strong light, at the same time that it is 

 freely exposed to the air. Usually, it is allowed to remain in this 

 position for twelve hours, when it is removed for observation, 

 and a fresh slip substituted ; but when there are indications of a 



