OCCURRING ON MALDEN ISLAND. 177 
Frigate Bird ( Tachepetes) Guano (recent). 
Water and organic matter... oe param 6 i: | 9°75 
Calcium phosphate ofa cs is .. 84°34 81°91 
>» carbonate .... a ade 2c ae ag COL 
2 sulphate 79 ; 
Magnesium carbonate, sleiKin, sun, “waa es 34 35 
100-00 100-00 
The organic matter present consisted principally of roots of 
plants, and yielded very small quantities of —— The removal 
of the nitrogenous organic matter appears, s island at all 
events, to be principally due to the action of “the heat of the sun, 
and not to rain, which is the cause usually assigned. Whilst 
‘the birds were on the ‘eek there was a considerable evolution 
ammonia ; but this disappeared entirely before they again 
laid, there being an interval of three months during which the 
seven showers—the heaviest being 0-4 inches, which fell about two 
or three days after the birds left the ground, and in e the 
nitrogenous matter had disap d before they returned 
guano seems*not to be deposited fast enough for the recent upper 
layers to protect the lower. 
The guanos deposited by the salt birds (puffinas) was always 
poor in phosphates, as they principally inhabited ground where 
dust—composed of carbonate and sulphate of calcium, deposited by 
the evaporation of the water of the lagoon—is deposited by the 
wind. By their continual burrowing they also bring up “is the 
surface portio _ deposi 
before they took possession of the ground. The following shows 
composition of some of this guano :— 
Water and organic matters. =... 20°66 = 26-24 263 
Phosphate of calcium __... ia .. 4090 5436 55°74 
baie seg pes ae 21 
The old guano is found on the low ground, a little mside the 
encircling ridge, and the surface is about 3 feet above water level. 
immediate surface is never of any value, gue largely contaminated 
with calcium carbonate ; and the richness in phosphates increases 
. With the depth. When the aD nak =. down tothe 
; lined indura very 
rich in phosphates (ernst guano of Vora loc. ney Of this I 
