566 Meeting! of the British Association. [Oct., 



future is less likely to act as an assistance than as a hindrance to 

 progress. Sir B. Brodie's theory is one from which the idea of 

 atoms is excluded, although it is by no means incompatible with 

 them. It is a system which involves a very great amount of 

 hypothesis, for the assumption of the compound nature of certain 

 of the elements is rendered necessary by Sir Benjamin's funda- 

 mental hypothesis. The question must at best be considered as 

 still sub judice, and the method is not likely to meet with general 

 acceptance until it is supported by a much larger body of facts than 

 those we at present possess. 



The most importaot paper read this day was one "On the 

 Decay of Stone, its Cause and Prevention," by J. Spiller. The 

 author has arrived at the conclusion that the corrosive action of 

 sulphurous and sulphuric acids in the atmosphere, resulting from 

 the combustion of coal-fuel, operates, in large towns especially, in a 

 very destructive manner upon dolomite and the numerous class 

 of limestones commonly employed in our public buildings ; this 

 chemical action, aided no doubt by the simultaneous attack of 

 carbonic acid and moisture, and in the winter season further 

 supplemented by the disintegrating effects of frost, furnishes a 

 sufficient explanation of all the facts observed. The best coal 

 and coke contain one per cent, of sulphur, equal to 70 lbs. of oil 

 of vitriol for every ton of coal burnt. This is the origin of the 

 sulphates invariably present in the loosened crust of decayed stones, 

 whether of calcareous or magnesian character. As a remedy for 

 the decay of stone, Mr. Spiller proposes the application to the 

 cleaned surfaces of the stone of an aqueous solution of superphos- 

 phate of lime, — a salt remarkable for its action in hardening the 

 surfaces of chalk, Caen stone, or other calcareous building stone to 

 which it may be applied, either by brushing or immersion, and 

 which acts upon the carbonate of lime in the stone, giving rise to 

 the formation of crystallized diphosphate of lime. 



The author brought forward some interesting results to record 

 in connection with the treatment of Portland stone, which serve to 

 illustrate the increased hardness and strength, and the diminished 

 rate and capacity of water-absorption, attending the employment of 

 the superphosphate. The cost of materials employed in the treat- 

 ment 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 coatings 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 solution, when diluted for use, should be about 1,100. 



