Study of the New York Obelisk as a Decayed Boulder. 139 



were heated, the melted paraffin applied, and the stone reheated. 

 A condensed statement of the observations is here presented. 



The temperature of the air was 6° C. (43° F.), which happens to 

 be about that which prevailed during the waterproofing treatment 

 of the Obelisk in 1885. In the treatment of Nos. 1, 2, and 6, the 

 charcoal-stove was applied, at a distance of 1 to 3 inches from the 

 surface; in that of Nos. 3, 4, and 5, the benzine blast-lamp, over a 

 surface of about 40 square inches. During the heating, a few sandy 

 particles fell from the decayed and softened surface. From the 

 totals, it appears that the entire treatment of a stone-surface, as 

 observed with several workmen, was completed, on the average, in 

 58 seconds. 



These results served as a basis for arrangement of a series of 

 experiments, carried on some weeks later, with the same process 

 and apparatus, in the north court of the old building of Columbia 

 College, at 50th Street, New York City. The treatment was 

 applied in the usual way to various surfaces of old brickwork, 

 covered with hard and dry cement-stucco. In each experiment a 

 thermometer was so inserted, beneath the stucco, that its bulb lay 

 at the depth of 3 mm. {^ inch) below the heated surface ; the object 

 was to determine the rise in temperature of the superficial layer of 

 cement. Temperature of the air, 15". 5 C. 



Source of 

 heat. 



Blast-lamp, 

 Blast-lamp. 

 Stove. 

 Stove. 



First heating. 



Period (in| Resulting 

 seconds), temperature. 



85 



55 



135 



50 



24° to 34° C. 



34° 



145 

 115 

 205 

 100 



