('OI.LKCrioNS IN KCON'oMIC (JKOI.OCSV AND M KTAI.LI lUJY. 213 



'I'hrei^ spt'ciiiU'iis illuslnitf llic leaclied guanos: 



(1) Somlircm, Hiitisli W'o.st India iHlunib (UvJTr)), of the ftillowiii;; DMiiiHtsitioii : 



MoiHtur«<, nt21:'^ (H,0) 



Wiitrr of conibinaliuii ( Hj( )) 



I'liospliuiif. ui'id * (P,Oii) 



Liiiio (<;ii()» 



Oxidu uf iron and nliiiuina ( (FeAI])0]) 

 Mat:n<'.sia, etc., uot det«rniinod (M^O). 



Ciirboiiic ncidt (CO/) .. 



Iiiitoliilile tiiiittcr 



a AualystA, O. H. Ogstun. 



?» Analysts, Aii;;ustu» Voolcker i. Sons. 



' K<niiil (« tribu.Hio plii).s|>hiUi) of lime, 76.38 iiiiil 71.81 pi-r i-mit. 



> E<|iial to oai'lioiiatt' 'if liiii<«. 12.95 per cent. 



(*.M S\v;in I.slaiul. (1(m;>((I. ) (•^) !Aw.u\ Ishui.l. ildf.-.-i.) 



KnNK llKPOSITS, 



Bone tlei)osits are ;neiierally loiiiid in cave.s, on the edjje.s ol" sliallow 

 lakes, and on some northern islands, especially where the penguin cou- 

 gn'<;ates. They consist of the bones of animals and birds which have 

 died tlieie or been brought by carnivorous animals. The deposits are 

 generally small. 



A single specimen is shown here. 



(1) Bonosot the peiigiiiii mixed with moss. Funk Island off Newfoundland. July 

 'J3. 1887. (G6581.) 



CLAYS. 



Under this head are included several well-defined minerals, some 

 doubtful and impure species, and various mixtures. They are applied 

 to a large variety of widely ditterent uses, so that it is impossible to give 

 a g«Mi(Mal deliriitioii. ('hemically they are all hydrated silicates of alu- 

 mina, Imt tiiey vary much in the relations between alumina, silica, ami 

 water, and are sometimes very impure. The most common impurity is 

 siliceous santl, and clays imperccptivcly graduate into samls. 



Nt'arly all days contain the mineral kaoliiiite as an essential con- 

 stituent, which, when pure, contains silica 4G.3 percent., alumina .'^9.8 

 |>cr c<'nt., water ^^t.'^ per cent. St)me of the i>urest days approa<-h this 

 composition, but all contain small amounts of other materials, especially 

 titanic acid, iron, and jiotash. Besides kaolinite clays frequently con- 

 tain (juartz, especially as sand, titanic acid minerals, fehlspars, micas, 

 pyiite, lignite, oxides, and carbonates of iron and other silicates. ( )cca- 

 sionally maiij' other minerals are found. A few clays do not contain 

 kaolinite, bill have tlie related mineral halloysite as a ba.sis. Ilalloy- 

 site when pure contains silica 13. .{ per cent., alumina 37.7 per cuiit., and 

 water I'.l per cent. 



