Septeiiihri-. 1!)2].| 



The Canadian Field-Xatckalist. 



115 



AN EXAMPLE OF GRAVITY DEFORMATION IX A LIMESTONE JSLAB. 



By E. M. Kindle. 



It is probably- not generally known that 

 cemeteries sometimes afford important 

 data concernino: the modification of certain 

 physical characters of prravestones which 

 may take place with the lapse of time. 

 In the erection of monuments the condi- 

 tions for highly instructive experiments 

 have been sometimes unconsciously pre- 

 pared. It is the purpose of these notes 

 to record the results of one of these for- 

 tuitous experiments in which gravity has 

 produced deformation. 



Numerous examples occur in nature of 

 the deformation of consolidated rocks pro- 

 duced by lateral pressure and gravity 

 combined; but no recorded cases of de- 

 formation produced by gravity alone un- 

 der natural conditions have come under 

 the writer's notice. In the experiments 

 of Daubree ^ Townsend -, Adams '', and 

 others, the great changes in shape which 

 can be produced in hard rocks and metals 

 by pressure have been shown, but experi- 

 ments in which gravity alone is the active 

 factor in defoi-mation have apparently' 

 been neglected because of the length of 

 time required. Experiments aiming to 

 produce rock deformation l)y the action of 

 gravity alone appear to have been under- 

 taken only in the case of ice. •*. 



Examples may occasionally be found in 

 cemeteries which give some definite in- 

 formation regarding the amount of flexing 

 which may result through the action of 

 gravity alone. Such cases are worthy of 

 record because they afford data on a phase 

 of rock deformation which can hardly be 

 approached experimentally, because of the 

 time required. 



(1) Etudes Synthetiques de Geologie Experi- 

 mentale, 1879. 



(2) Jour. Franklin Inst., Mar. 1878. 



(3) Geol. Soc. of Am. Bull., Vol. 12. pp. 45.")- 

 461. 



(4") Von P^nseln, O.D.. Experimental Studies 

 and Observations on Ice Structure, Am. Jour, 

 of Sci., 4th. ser., Vol. 40. pp. 459-460. figr. 7. 

 R. S. Tarr and O. D. von Engeln, Experimen- 

 tal Studies of Ice with reference to Glacier 

 Structure and Motion, pp. 82-139, fig. 9. Zeit- 

 schrift fur Gletscherkunde. Bd. Ix. 1915. 



King \ Ashley ^ and the writer \ have 

 desf;ribed examples of permanent flexing 

 in marble slabs which have been supported 

 by the ends. Becker ^ has noted in old 

 buildings such as the Alhambra ".slabs 

 of rock very much bent by end pressures 

 acting for hundreds of years." 



Previously recorded observations on de- 

 formation in cemetery monuments all re- 

 fer, with one exception, .so far as the writ- 

 er is aware, to marble slabs. The excep- 

 tion, if it may be .so termed, is described 

 by Winslow^ as a white crystalline lime- 

 stone or marble. 



It is purposed to call attention here to 

 the case of -a limestone slab covering a 

 grave in a cemetery in Hull, P.Q. In 

 the example under consideration the stone 

 is an unaltered limestone of Trenton age 

 as indicated by the fossils which it con- 

 tains. 



During the early history of the Ottawa 

 Valley slabs of Trenton limestone were 

 sometimes used for monuments in the local 

 cemeteries. In the Hull cemetery there 

 is a slab of Trenton limestone over one 

 of the fir.st graves made in this cemetery 

 which is supported on two upright stones 

 placed under the two ends, the middle 

 portion of the slab being subject to gravi- 

 tational pull without any support. This 

 has developed in the middle portion of the 

 slab a sag amounting to 11/2 inches. The 

 general appearance of this slab is sho^vn 

 in the accompanying photograph (Fig. 1). 

 This slab has a lengl.li of 6 ft. 6 in., a widt^i 

 of 2 ft. lOVii ill- tiiid a thicknes.s of 3% ^^^ 

 The inscription on the face of the stone 

 indicates that it was placed in position in 

 1844 or a little later. The deformation 

 which this slab of Trenton limestone has 

 suffered has been developed tlieiefore dur- 

 ing a time interval of not more than 77 

 years. 



(5) U. S. Geol. Exp., 40th. Par.. Vol. I. p. 752. 

 (fi) Proc. Cal. Acad. Sci., Vol. 3. 2nd. ser.. 

 1890-92 (1893) pp. 319-324. 



(7) Proc. Ind. Acad. Sci.. 1894. pp. 49-50. 



(8) Geol. Soc. of Am. Bull , Vol. ^V^ 1893. 

 1). 53. 



(9^ Am. Jour. Sci., Vol. 43. 1892. pp. 133- 

 134. 



