ON THE DECAY OF STONE. 
385 
I. 
II. 
Stone in original condition . 
5 > 5 ) 
III. 
IV. 
Mean . 
Stone treated with superphosphate 
>5 >> J) 
Mean . 
Crushing Weight. 
. . 3650 lbs. 
. . 3800 „ 
. . 3725 „ 
. . 5375 lbs. 
. . 5500 „ 
. . 5437 „ 
Thus acquiring an increased strength, amounting almost to 50 per cent. The relative 
hardness of the stone before and after treatment could be readily ascertained by mutual 
friction of their surfaces, and also by scratching with a pointed instrument of copper, 
which metal proved to possess a degree of hardness intermediate between the original 
and treated Portland stones. 
The porosity of the stone as indicated by the amount of water absorbed in equal in¬ 
tervals of time proved to be greatly diminished in the case of the treated cubes. On 
this point several experiments were made, the stone being first weighed in the air-dried 
condition, and then immersed in distilled water at the temperature of 60° F. for the 
several periods named, and the increase of weight in each case noted. 
“ Whit Bed ” Portland . 
Treated stone. 
Gts. 
. 1420 
7 
8 
. 12 
. 25 
Grs. 
. 1335 
. 20 
. 33 
. 50 
. 78 
These results have been further controlled by other experiments in which the same 
Hock was used in the original condition, and again after treatment with the superphos¬ 
phate. It will be noticed that the advantage of the process is most clearly apparent in 
the case of the denser and more compact variety of Portland known as the “Whit Bed,” 
which alone is employed for external building purposes ; the other—the “Base Bed”— 
is softer and only fit for internal decoration, and its texture is so porous that in becom¬ 
ing saturated it absorbs nearly 10 per cent, of water. 
Samples of Mansfield dolomite absorbed amounts of water varying in different speci¬ 
mens from 6 to 8 per cent. After treatment by my process the degree of absorption was 
reduced one-half; and the results were even more favourable in the case of Caen stone. 
The cost of materials employed in the treatment of stone according to this plan is 
very trifling, and bears but a small proportion to the cost of labour necessarily expended 
upon the cleaning and preliminary preparation of the stone before the solution can be 
applied. One gallon of solution will cover about 300 feet superficial, when two coat¬ 
ings are applied upon Caen or Portland stone. The superphosphate employed must not 
contain any appreciable amount of sulphuric acid, and the specific gravity of the solu¬ 
tion, when diluted for use, should be about 1100. 
The facts now stated have, it is believed, but a minor interest for the inhabitants of 
these parts of the United Kingdom ; for with Aberdeen granite and Craigleith sandstone 
at command, there will be no need to resort to chemical methods of preservation. 
Weight of cube (dry) 
Water absorbed in 
55 
55 
J) 
55 
J) 
55 
yy 
yy 
5 min 
15 „ . 
30 
yy 
„ 1 hour 30 „ 
Original stone 
Grs. 
1421 
70 
91 
91 
92 
“ Base Bed ” Portland. 
Grs. 
"Weight of cube (dry).1291 
"Water absorbed in 5 min. . 120 
15 „ . . 122 
yy 
yy 
yy 
yy 
yy 
yy 
yy 
yy 
„ 1 hour 30 „ 
30 
124 
126 
2 o 
YOL. IX. 
