146 



CHEMICAL ACTION. 



the coast. It is probable that any attentive obser- 

 ver would not estimate the loss of land there at less 

 than this amount. Nearly one half the matter com- 

 ing from the degradation of the land is supposed to 

 be swept coastwise in a westerly direction. There 

 are many evidences that the east end of Long Isl- 

 and was once much larger than at present; and it 

 is thought probable that it might have been connect- 

 ed with Block Island, which lies in the direction of 

 the prolongation of Long Island." 



Chemical action. — Rocks are continually subject to 

 decomposition, through the influence of chemical 

 changes. Chemical affinity is constantly and suc- 

 cessfully acting against the attraction of cohesion ; 

 in other words, the forces which strive to separate 

 the particles of rocks are superior to those which 

 tend to bind them together; the consequence is a 

 silent, but sure, and often a rapid, decay of the solid 

 structure of the globe. " It is painful," says Philips, 

 " to mark the injuries effected by a few centuries 

 on the richly sculptured arches of the Romans, the 

 graceful mouldings of the early English architects, 

 and the rich foliage of the decorated and later Gothic 

 styles. The changing temperature and moisture of 

 the air communicated to the slowly conducting.stone, 

 especially on the western and southern fronts of 

 buildings, bursts the parts near the surface into pow- 

 der, or, by introducing a new arrangement of the 

 particles, separates the external from the internal 

 parts, and causes the exfohation or desquamation, as 

 MacCulloch calls it, of whole sheets of stone paral- 

 lel to the ornamental work of the mason. From 

 these attacks no shelter can wholly protect; the 

 parts of a building which are below a ledge often 

 decay the first ; oiling and painting will only retard 

 the destruction ; and stones which resist all watery 

 agency, and refuse to burst with changes of temper- 

 ature, are secretly eaten away by the chemical forces 

 of carbonic acid and other atmospheric influences. 



