Study of the New York Oheliak as a Decayed Boulder. 135 



monument per annum to be 0.457 gram, or, from the entire wasting- 

 surface, 10.88 grams; and estimated that if "the mass of fragments 

 actually collected was not more than a tenth part of what had fallen 

 during the time the Obelisk has been in our Park, it would still 

 require 6000 years to reduce its volume to the depth of one centi- 

 meter on each side." 



During the next year, 1884, the progress of the decay became 

 still more manifest by the flaking away and fall of fragments, some- 

 times of considerable size. Commander Gorringe could hardly be- 

 lieve that they came from the monolith, and expressed the hope that 

 some day it would be polished. 



In the autumn of the same year, the attention of the Park Com- 

 missioners was directed to this serious decay, and they finally 

 decided to make use of a waterproofing process, founded on the 

 application of melted paraffin to the artificially warmed surface of 

 the stone. This was begun on September 25, 1885, after the Obe- 

 lisk had stood, entirely unprotected from the elements, for 4 years 

 and 8 months after its re-erection. 



In the notes of another observer,^ made at this time, on the 

 weathered exterior of the Obelisk, it is stated : " Most of the frac- 

 tures of the flakes seemed of recent origin, although under most of 

 them was found a green vegetable growth of unicellular plants. 

 However, beneath some pieces, the accumulated black dirt showed 

 the fractures to be of more remote origin. . . . Placing a fragment 

 of the rock under the microscope, portions of it show decided dis- 

 integration, parts of the hornblende being broken down and dis- 

 solved, while some of the white feldspar is broken into such minute 

 fragments that they exhibit the Brownian movement when placed 

 in water. In the minute crevices can be seen the green cells of 

 vegetable growth, and, on either side of the crevice, may sometimes 

 be seen, with the microscope, the rosy hue indicating internal strains 

 in the very minute fragments, a slight increase of which would 

 complete the fracture ; and it is possible that the growing cells may 

 furnish the necessary strain." All these vegetable cells were green, 

 some rod-shaped, others round like those of Frotococcus pluvialis. 



On the S.S.W. side of the shaft, where the decay was most pro- 

 nounced, some of the adhering flakes of rock were found to be 

 parted above from the shaft as much as one-quarter of an inch, a 

 crevice of that width being sometimes found filled with moss and 

 black earth. 



1 Dudley, loc. cit., 67. 



