Trans. N. V. Ac. Set. ^6 /««• 29, 



limestone, all in good onclition, and white marble, in a decided state 

 of decay. 



The artificial methods of trial of stone, now occasionally in vogue, 

 whenever some extraordinary pressure is brought upon architects to 

 pay a little attention to the durability of the material they propose to 

 employ, are, from their obsolete antiquity, imperfection, or absolute 

 inaccuracy, unworthy of the age and of so honorable a profession. They 

 usually consist of trials of solubility in acids, of absorptive power for 

 water, of resistance to frost, tested by the efflorescence of sodium- 

 sulphate, and of resistance to crushing. The latter may have the re- 

 motest relationship to the elements of durability in many rocks, and yet 

 is one on which much reliance of the architectural world is now 

 placed. Sooner or later a wide departure will take place from these 

 incomplete and antique methods, in the light of modern discovery. 



Reference was made to certain experiments by Prof. J. C Draper on 

 the brownstone and Nova-Scotia stone used in this city, by Dr. Page on 

 a series of the building-stones, and by Profs. J. Henry and W. R.John- 

 son on American marbles, in some cases w'ith conflicting results, which 

 were probably due to the limited number and methods of the experi- 

 ments. 



V. Means of Protection and Preservation of Stone. 



We have here to consider certain natural principles of construction, 

 and then the methods tor the artificial preservation of the stone used 

 in buildiifgs. Under the first head, there are four divisions. 



Selection of stone. As it is universally agreed that the utmost impor- 

 tance rests upon the original selection of the building-material, it is here 

 that all the resources of lithological science should be called in. Only 

 one investigation, aiming at thorough work, has ever been carried 

 through, that of the Royal Commission appointed for the selection of stone 

 for the Houses of Parliament. But the efforts of these able men were 

 restricted by the little progress made at that time in the general study 

 of rocks, and were afterwards completely thwarted by the discharge of 

 the Committee and by the delivery of the execution of the work of 

 selection to incompetent hands. There will be hereafter, from investi- 

 gations made in the light of modern researches, no excuse for such an- 

 noying results and enormous expenses as those which attended the end- 

 less repairs which have been required, since a period of four or five years 

 after the completion of the great building referred to. 



Seasoning. The recommendations of Viturvius, 2000 years ago, have 

 been observed at times down to the day of Sir Christopher Wren, 

 who would not accept the stone, which he proposed to use in the erec- 

 tion of St. Paul's Cathedra], in London, until it had lain for three 



