ON TUi: Ui:0L0GY OF liAillJADOS. 213 



and this variety is locally called "marl''; the portions which arc 

 quarried for building-stone consist of a firm but light and i)orous 

 rock, which forms what would be called a freestone in England, but 

 in Barbados is generally termed " sawstone.'" This is not an oolite, 

 but consists mainly of coral-sand and shell-debris with some 

 scattered corals, but the quarrymen naturally select the parts where 

 lumps of coral are fewest, and where the rock is of fairly even 

 grain. 



Above the 300-feet level the rock is often hard and compact, and 

 is capable of being used for mending the roads, but in other places 

 it is of a loose and rubbly nature, due apparently to the abstraction 

 of material by percolating water. 



Eoth above and below the 300-feet level the harder and softer 

 varieties of stone often alternate one with the other ; here and 

 there hard layers occur which form floors across the roadway, and 

 require a heavy blow to break them ; some of these layers appear 

 to have been formed by a growth of hard compact nullipore-rock 

 ill situ, others are simply fine chalky sediment which has been 

 compacted by the infiltration of a calcareous cement. Where the 

 grain is coarser the differences of hardness are doubtless due to 

 the different action which the percolating waters have had at 

 different places and levels. In places where the water has had 

 a free flow it has abstracted material and carried it away in 

 solution, but where the flow has been checked, or it has had to 

 pass through a bed of finer grain, some of the dissolved carbonate of 

 lime seems to have been deposited in the form of a calcareous 

 cement. 



In tropical countries notice must be taken of the capillary action 

 set up in the subsoil hj the rapid drying of the surface in the sun's 

 heat. Thus, after a shower, the rainwater sinks into the ground, 

 and dissolves a certain amount of limestone, but on those spots 

 where the heat of the sun is concentrated, and especially where 

 the surface of the soil is bare of vegetation, a reverse action must 

 after a time be set up, the sun's heat evaporating the moisture 

 from the surface, and causing capillary currents from below and 

 from the sides of the drying area. The water thus drawn upward 

 from the rock will contain carbonate of lime in solution, which 

 material will bo deposited in the interstices of the rock as the 

 water itself is evaporated, AVe have noticed that the bare surfaces 

 of coral-rock, especially on the higher parts of the island, generally 

 have a very hard crust, which is not an external accretion, but an 

 indurated portion of the rock, and we attribute this to the deposi- 

 tion of carbonate of lime by the process above indicated. In these 

 districts the rock is often appreciably hardened for several feet from 

 the surface, but at a certain distance becomes quite loose, porous, 

 and easily quarried. 



At the Crane, in the 8.E. of St. Philip's parish, the shore-line 

 consists of cliffs of coral-limestone, which exhibit to a greater 

 extent than elsewhere the differences which we have described as 

 due to the partial solution ami redeposition of the limestone. South 



