80 



"The object of these experiments is this: Seeing that the 

 nattu'al moisture of a quarry, which masons call the 'sap' of the 

 stone, or its tendency to absorb wet, seems to be the chief 

 cause of its tearing and wearing away 'in frost, what I do is 

 this : — I get samples fresh from different quarries, have them 

 gauged to six- inch cubes, weigh them accurately, dry them 

 artificially and by exposure to sun and air, and continue 

 weighing them every morning and evening, till they come to a 

 fixed weight; I then immerse some in water, and expose some 

 to wind, rain, &c., and go on weighing. 



"Of the Painswick stone, which alone I have tried lately, one 

 sample which weighed 181b. 4oz., gained only 2oz. by soaking in 

 rain-water for five days; while another, which weighed 181b. 8oz. 

 on coming out of the quarry, sank to 171b. in ten days' exposure 

 to sun and wind, with ten nights on the hot-plate in the kitchen; 

 and what was curious, was, that one day, after a night on the 

 hot-plate, during a hot sun and wind, it gained 2oz. from the 

 air, showing that it absorbed moisture very readily, although 

 there was not a drop of rain. This experiment shows also that 

 Painswick stone in its natural state is nearly saturated with 

 moisture. This was the general result I obtained before, but 

 of comparative details I remember nil. I acted upon it when I 

 made additions to my house. I had the stone quarried and 

 worked-up ready to go in the building the year before, keeping 

 it in a covered shed open on the sides. That stone I used in 

 any dangerous positions for stone not considered weather-stone. 

 It has now been exposed since 1827, with scarcely an imperfection 

 — I may, indeed, say none, except in the horizontal surface of 

 the coping on the parapet, which has required restoration. But 

 I used none within reach of the absorption from the ground, 

 and laid it all on its natural bed; and this may account for the 

 giving of the coping, which, I am told, masons within a few 

 years past, used to lay with the edge of the natural bed as the 

 top surface. 



"Another precaution which, I am told, is put in practice 

 now, is to use the saw, in preference to a heavy axe or broad 

 chisel ; everything which jars the fibre, as it were, gives it a 

 tendency to suck up moisture, and to disintegrate with frost. 



