66 TRANSACTIONS OF THE [NOV. 33, 



cation, acquired by many years of experience, it was safely ac- 

 coinplishcd, and I do not think that a single particle of "solid 

 sound stone was displaced from the surface of the obelisk, by the 

 application of the heat employed to enable the stone to absorb 

 the conijiound to an effective depth. There were many witnesses 

 to the correctness of this statement, some of whom watched 

 especially for it. There were even spaces that Avere hollow be- 

 neath that were successfully treated. In some few instances 

 where the pieces were very loose and had a green vegetable 

 growth behind them, as soon as the stove had warmed the stone, 

 the steam came out of the humble but audacious plant-life at 

 the back of the loosened scale, and these pieces we removed. 



I believe the compound penetrated to a depth of half an inch 

 and deei)ei-. The stone certainly absorbed it in considerable 

 quantities, no less than G7f pounds having been used. The 

 surface treated — shaft and plinth — is about 220 square yards. 

 An equal surface of brownstone would have taken from 40 to 

 50 ])ounds. I'he work was effectually accomplished, and nothing 

 was spared to insure a satisfactory result. 



We did most of the work when the wind was bTowing a gale 

 from the northwest, and one squall that passed left our top i)oles 

 covered with ice, though below it was simply a cold rain. 



DISCUSSION. 



Mr. Caffall, in answer to inquiries, said that ordinarily one 

 joound of the paraflfine compound would cover two to three square 

 yards of brick surface. The compound ])enetrates the stone only 

 as far as the melting-heat penetrates. If some of the liquid i-e- 

 mains upon the surface, it demonstrates that the pores of the 

 brick or stone are completely filled to the depth reached. 'LMien 

 a reheating causes the absorption of this excess, and leaves the 

 surface clear. By this method, the thickness of the saturated 

 layer is under control. The melting-point of the compound is 

 140° F. It consists of parafline, containing creasote dissolved in 

 turpentine. The use of creasote prevents organic growth upon 

 the surface. The compound, in its constituents and its propor- 

 tions, is the result of many experiments and long experience. 



Prof. K. Ogden Doremus called the attention to the state- 

 ment of Prof. Persifor Frazer concerning the rock of the obelisk, 

 contained in the eighth chapter of Commander Clorringe's work 

 on " Egyi)tian Obelisks," and read as follows: ''The first thing 

 that strikes one is the freshness and soundness of the rock. Ko 

 maladie de granite is observable, and this fact will answer the 

 first and natural (piestion as to why this rock was so much pre- 

 ferred by the Egyptians for monumental purposes." Again, 

 on page 167 Prof.Frazer says: "The rock of the Needle can^ 



