Stvdy of the New York Oheliak as a Decayed Boulder. 151 



parts by a deep cleft. Onr application to Mr. William D. DeWitt for 

 its use met with his ready consent, and whatever help we needed/" 



In the ensuing experiment, the Committee had two points in 

 view : — 



First, "to determine the rate of penetration of a definite amount 

 of heat into a huge mass of granite, when applied continuously to a 

 small spot on one surface." The practical object w^as to ascertain 

 the time needed to bring the temperature of a layer of the granite, 

 one to two inches in thickness, up to or a little above the melting- 

 point of paraffin, without injury to the stone. 



Secondly, to determine the most effective way, and proper appa- 

 ratus, for the application of melted paraffin, to cause the deepest 

 penetration and thorough saturatioji of the warmed stone and of 

 any cavities or crevices lying beneath its surface. 



(1). The application of heat. — The N.E. corner of the huge 

 boulder was selected for the main experiment, where two vertical 

 faces, approximately even and smooth, met nearly at a right angle. 

 The N. face presented, in cross-section, the edges of the vertical 

 laminae of the gneiss. The E. face was reserved for the application 

 of the heat, and on the N. face, at a point about 6 feet above the 

 ground, a series of 13 horizontal boles, about 2 cm. in diameter, were 

 drilled at right angles to the face, each to the depth of about 10 inches, 

 for the insertion of a set of thermometers in a sloping line. The 

 direction of these holes was controlled by means of an instrument 

 constructed on the principle of parallel rules ; by this also the exact 

 distance was ascertained between the bottom of the hole, where the 

 bulb of the thermometer would lie, and a marked spot on the east 

 face of the boulder, 10 inches south of the corner The holes were 

 arranged in a line sloping upward at an angle of about 45°, with the 

 purpose that every thermometer-bulb should lie horizontally behind 

 the warmed spot on the east face of the boulder, and yet without the 

 interposition of any other of the bored holes and interference with 

 heat-waves which might thence result. Into these holes the set 

 of long delicate thermometers, with open Centigrade scale, were 

 inserted and firmly packed with soft asbestos-w^ool or cotton, so 

 that their bulbs were arranged at the following successive distances 

 from the east face, 1.7, 2.4, 2.8, 3.1, 4, 4 8, 5.6, 6.5, 8.3, 24.6, and 

 50.1 centimeters : and so that the degrees above 20° C. were visible 

 at a glance, upon the projecting parts of the scales, from an observer 

 on a small platform near the corner on the north side. 



In front of the east face a shears was erected, supporting the 



