2 



" The following analyses will give an idea of the composition of good commercial samples of the- 

 Cayman Phosphate Rock : — 





a. 



b. 



Moisture 



4.34 



3.66 



Organic matter and loss on ignition 



4.56 



5.76 



Sand &c. insoluble in Hydrochloric Acid 



0.17 



2.0o 



Alumina Al 2 3 



1.41 



6.20 



Ferric Oxide Fe 2 3 



067 



3.43 



Magnesia MgO 



0.70 





Lime CaO 



48.30 



43.85 



f Carbonic Acid C0 2 



2 89 



3.03 



* Phosphoric Acid P 2 5 



36.96 



32.16 





100.00 



100.14 



f Equivalent to Carbonate of Lime 



6.57 



6.90 



* " " Phosphate of Lime 



80.70 



70.20 



" The Cayman phosphate is evidently the result of theaction'of water; samples are frequently found 

 with considerable resemblance to Agate showing a banded structure due to intermittent deposition from 

 solution. Nor have these phosphates been exposed to much if any change since their formation, they 

 therefore remain in a comparatively soft condition, rendering the phosphate more soluble in water, and 

 especially in water charged with carbonic acid, than are apatite or other more changed and hardened 

 phosphate of lime. Hence the special value of the Cayman phosphate as a manure, without further 

 treatment than simple powdering. 



" I have not seen the Cayman phosphate in situ but judging from the samples I have examined, and 

 the accounts given by those who have visited the Islands in search of phosphates, I have no doubt they 

 have been formed in the same manner as the phosphate of lime upon the Pedro Cays. These latter I 

 have studied, having twice visited the Cays, on each occasion spending several days upon them. The 

 mode of formation appears to be as follows: — The Cays are formed of coral limestone and much of 

 their surface is covered with coral sand. Enormous numbers of terns resort to these Cays during the 

 nesting season; their eggs are brought to Kingston and sold here as booby eggs. Other sea birds in 

 smaller numbers live upon the Cays all the year round Crabs of various kinds swarm upon them at 

 night spreading over every part of the islands ; I have seen the ground in some places completely covered 

 with their dung. Much rain falls upon the Cays, the rain water dissolves the soluble alkaline phos- 

 phates out of the more or less decomposed bird and crab dung. This solution percolates through the 

 limestone or coral sand giving rise to a double decomposition, whereby the limestone parts with car- 

 bonic acid taking phosphoric acid from the solution in its stead. Thus carbonate of lime, i.e., lime- 

 stone, coral sand, &c, is converted into phosphate of lime. No doubt the rain water also removes 

 much carbonate of lime by direct solution thus aiding the accumulation of phosphate of lime. 



" That this is the manner in which the phosphate of lime is formed is evident from the following facts. 

 One portion of one of the Cays is free from coral sand, its surface consisting of bare rock, here the 

 true booby habitually lives and breeds, and the surface of the rock, if not recently disturbed, will be 

 found to be phosphate of lime mixed with a little organic matter but free, or nearly free, from car- 

 bonate of lime. The deeper one digs into the rock the smaller the proportion of phosphate and the 

 larger the proportion of carbonate, hence in mining phosphate care must be taken not to remove too 

 great a thickness of the rock. Again I found large surfaces of rock of paying quality to a depth of 

 from 6 to 18 inches ; the men employed in digging the phosphate assured ma that that same area had 

 been dug many years before and all paying phosphate removed. Plainly more had been formed in the 

 interval preceding my visit. The same holds good for the portion of the Cays covered with coral sand r 

 the upper layers are always the richest in phosphate ; in digging, pure coral sand, without admixture of 

 phosphate, is speedily met. Here agram areas which have been exhausted of phosphate are found in 

 time again to yield a surface layer of paying percentage. 



" The similar action at the Caymans I think took place at a much earlier period, and possibly is now 

 going on, but it was carried out to a much greater extent than on the Pedro Cays; as is evident from 

 the amount of red clay on the Cayman Islands, this red clay being the residue from immense quantites 

 of carbonate of lime removed in solution. 



7. The plants which I collected, were sent to Kew, and I am indebted to the authorities there for 

 their determination. The list of their names is added in an Appendix, and I have supplied notes of 

 their geographical distribution. From this list it will be seen that about 20 per cent, of the species are 

 found more or less throughout the Tropics. They are such as one might expect to find on any tropical 

 island. It is interesting to note that one of the ferns ( Acrostichum aureum) which is found growing to 

 a height of 6 to 10 feet in swamps in Jamaica and throughout the Tropics, is one of the first plants to 

 establish itself on the Island of Krakatao, where a terrible volcanic disturbance a short time ago com- 

 pletely destroyed every vestige of plant life. On its shore was also found the fruit of another plant 

 occurring in the Cayman Islands, viz., the " Almond Tree" ( Terminalia Catappa.) The gulf stream and 

 equatorial current will to some extent account for a number of American and We3t Indian species. 

 About 35 per cent, are found elsewhere in tropical America and the West Indies, more than half of 

 which are found widespread over this region; others are more confined in their distribution, for instance 

 Cassia ligustrina, is recorded only from Guiana besides the West Indies ; others stretch beyond the 

 region, one of the verveins ( Strachytarpheta jamaicensis) being also found in Florida. About 16 per 

 cent, also occur in parts of the West Indies and Central America, 14 per cent, in the West Indies, of 



