A. Gray—Do varieties wear out, or tend to wear out? 109 
The possibility of converting granite into serpentine. 
The possibility of converting granulite into serpentine. 
The possibility of converting gneiss into serpentine. 
The possibility of converting diorite into serpentine. 
The possibility of converting limestone into granite. 
10. The possibility of converting limestone into gneiss. 
Again, with the exception of the year 1858, I have never 
held nor taught that metamorphism is pseudomorphism ona 
broad scale. My Geology gives a very different definition of 
metamorphism. 
Oo SS ST 
I regret that I have been compelled to return to this un- 
pleasant subject. Charged with holding views which I did not 
entertain, it became a duty to the cause of scientific truth to 
ut in a disclaimer. And now that Mr. Hunt’s misstatements 
ave been given new currency by a republication of them, with 
additions, in his volume of Essays, and since his repeated asser- 
tions have led to my being quoted for the views attributed to 
me, a new explanation and denial seemed to be demanded. 
The case is a strange one in the annals of science. Four 
years have not sufficed to secure a recognition of the facts. 
Any other person, with hardly an exception, if he had had my 
denial, and had been referred to publications of mine that gave 
my views and fully sustained the denial, would have accepted 
the statement, and made a public correction. The misrepre- 
Sentations are a blot on the volume of Essays, and one which 
might have easily been avoided. 
ee KUL Dy Variekes wear out, or tend to wear out? By 
Professor ASA GRAY. 
are following article was published in the N. Y. Tribune, (the 
D 
the author, Although cast in a popular form, for general readers, 
Wwe deem it well worthy of reproduction in this Journal.—Epbs. 
Tuts question has been argued from time to time for more 
than half a century, and is far from being settled yet. Indeed, 
4 'S not to be settled either way so easily as is sometimes 
Hought. The result of a prolonged and rather lively discus- 
