J..D. Dana on Lettering figures of Crystals. 399 
lar rings indicate an age of about 300 years. Owing toa slight 
decay they cannot be counted with exactuess. 
There is or was, a few years siuce, an elm a little more than 
33 feet in circumference, standing about a mile from the village 
of Auburn in this state.. It was a few reds from the tumpike. 
oe attained quite a celebrity and was long kuown as the “big 
elm.’ 
In the township of Sodus, Wayne county, are many large 
sycamores ( Platanus occidentalis ), several of which are from 14 
to 16 feet in diameter. The largest of them are uniformly hel- 
w. ‘These trees are not far from Lake Ontario and their 
branches still appear to be in a flourishing condition. f 
the trees named in the foregoing article grew in a rich deep allu- 
vial soil; even the large pines were either in raviues or valleys. 
Art. XL.—On Lettering figures of Crystals; by James 
D. Dana. 
A concise method of lettering figures of crystals so that the 
exact positions of the planes with reference to the axes shall be 
indicated, would, if adopted, aid much student in compre- 
hending the subject of crystallography, a give him almost 
without-effort an insight into its satinatice! department. The 
that work for witoe tiation if not eatt wil the sahiect. We 
merely add that the planes are expressed by a ee Sprite oe. 
their Position with reference to the axes, as fy 
=: : 3:2, or in general terms, m:n:r, the first figure 
referring to the vertical axis axis a), and the pibiens to the lateral 
band c): 6:3: 2, or 6a: 3b: 2c, signifying that the plane so 
esiahiiil: referred to the three axes, meets (or would meet if 
extended) the vertical axis at a distance 6a, one lateral at a dis- 
tance 36, and the other at a distance 2c, or in this ratio. 
