36 The American Geologist. January, 1904. 
men of the city. Samples were sent to the U. S. Department of 
Agriculture, the Na'lional Museum, the state geologist and the 
State Agricultural College. All gave favorable opinions of its 
probable value for ornamental and monumental purposes. 
Dr. Geo. P. Merril, head curator of department of geology 
in the National Museum, says : "The sample of rock forward- 
ed belongs to the basic igneous class, commonly known as gab- 
bro. In general appearance this rock bears a close resemblance 
■ to the gabbro quarried near Addison, Maine, and commercially 
known under the name of black granite. The mineral consti- 
tuents of this rock are plagioclase feldspars, augite, biotite, and 
magnetite or titanic iron, together with microscopic apatites. 
In this respect it differs somewhat from the Addison stone, 
which carries also the minerals hypersthene and olivine. The 
Quincy, Barre, and St. Cloud granites differ from the sample 
submitted, in that they all carry orthoclase feldspars and free 
quartz. 
"As to the weathering of this particular sample forwarded, 
I cannot speak too definitely from a mere inspection of the 
sample. Rocks of this class vary greatly in their weathering 
properties. The Addison, Maine, rock which it closely resem- 
bles, has been found by experience to be exceedingly durable 
and in all respects a most excellent stone. I am not quite so 
favorably impressed with the sample you forward, owing to its 
great richness in magnetite, which while not at all injurious in 
small quantities, may prove so where existing so abundantly. 
I might suggest the best method in your locality would be to 
inspect natural outcrops, and particularly the glaciated sur- 
faces, if such exist. If the rock, where it has been exposed to 
the action of the atmosphere since the passage of the ice-sheet, 
still shows glacial polishing and stride without serious discolor- 
ation, it is pretty good indication that the stone will be suitable 
for all human requirements." 
Secretary Wilson of the Department of Agriculture having 
submitted it to the chemist of the department, reports : "The 
rock is commonly known as trap, and scientifically as diabase. 
It is composed essentially of feldspar (labradorite) and au- 
gite, and contains about ten per cent iron ore (magnetite) 
which is the cause of the rock rusting on exposed surfaces. The 
rock is of igneous origin and occurs usually in large masses, 
