/. D. Hague on the Guano Islands of the Pacific Ocean. 235 



I have said that there was beneath the crust a stratum of gu- 

 ano of variable depth. Frequently it is wanting altogether, the 

 whole being taken up in the crust and lying in immediate con- 

 tact with the bed of gypsum. Where there is such a layer of 

 guano it is variable in composition, being mixed with more or 

 less sulphate of lime. 



It generally contains from sixty to seventy per cent phosphate 



I come now to speak of that part of the Jarvis deposit which 

 rests on a coral foundation. This is of limited extent, but is of 

 great interest because of its similarity to the Baker guano. It 

 is about two feet deep; is a dry powder of dark brown color, of 

 rather lighter shade than the Baker guano, owing to the pres- 

 ence of less vegetable matter. It contains very little coral sand 

 mixed with it. The following is an analysis: 



Moisture at 212° Falir., 5-02 



Carbonic acid ■ '81 



Chlorine, alkalies, iron, etc., ^'^^ 



It is important to observe that while the greater part of the 

 Ji^rvis guano, as already described, differs materially from the 

 Baker, this portion of the Jarvis deposit has almost the same 

 chemical and physical characteristics as the Baker or Howland 

 guano. Restinc^ like that on a coral foundation, it has been ex- 

 posed only to ifke influences, while the Jarvis crusted deposit, 

 above described, owes its peculiar character to its contact with 

 tlie gypsum on which it lies and to the action of the sea water. 



This gypsum or sulphate of lime is usually soft and amor- 

 phous, sometimes crystalline, and, at a depth of eighteen inches 

 or two feet, occurs in hard, compact, crystalline beds. It is of a 

 %lit snuff color, and where it underlies guano, is ™xed with 

 considerable phosphate of lime, which has been washed down 

 from the surface. Similar deposits of sulphate of lime occur on 

 ttiany other elevated lagoon-islands of the Pacific, some ot which 

 I shall allude to below. I have also seen gypsum ^^ ^^""Jj^^ 

 character and appearance, which occurs in ; Pf^^'^^^i^''";^^^ 

 Repressions in the now elevated portions of the coral reef at 

 O^hu, Sandwich Islands, and doubtless due to the same source, 

 "le evaporation of sea water. , -r 



^^ Unfortunately for the commercial interests of the Jarv-.s guano^ 

 the earlier cargoes (the first one or two) that ^f ^.^^-^j^f ^^^^^^^ 

 ^ere selected without the aid of chemical analysis, and tho^e in 

 charge mistaking the gypsum for guano, sent home cargoes, tne 



