io8o 



son, PHYSICS, CIIKMISTRY AXD MICROBIOLOGY 



ther limited ; it has not been attacked by any disease ; two breeds are rear- 

 ed, one with yellow, the other with white silk. Crosses between these two 

 have also been made. In Trinidad there is a wild silkworm, Attacus Hesper- 

 us, which feeds on the leaves of Casearia sp. ; it can be reared artificially^ 

 but the moths must be enclosed in cages for mating and oviposition. 



Specimens of cocoons of Bomhyx mori (yellow and white), Attacus ri- 

 cini and Attacus hesperus examined at the Imperial Institute were found to 

 be of good quality. 



There is no doubt that silkworm rearing can be successfully established 

 in Trinidad. Of the different species there tested, those yielding the best 

 results are Bomhyx mori, and especially Attacus ricini, which stands higher 

 temperatures and furnishes more easily handled cocoons. 



SOIL PHYSICS, 



CHEMISTRY 



AND 



MICROBIOLOGY 



CROPS AND CUIvTIVATION. 



842 - On the Origin ofRedSoil". — Manasse E., in GiomalediGeologia Pratica. Xlllth 

 Year, Part IIl-IV, pp. 101-103. Parma and Pisa, 1915 (i). 



Trial analyses were made of two red soils from the " Montagnola " 

 of Sienna, namely, a complete analj^sis, treatment with hydrochloric acid 

 in the presence of kaolin, attack by sulphuric acid, solubility in hot dilute 

 potassium hydroxide. From these experiments it would appear that : 

 i) the alumina to a fairly large extent, almost the whole of the ferric oxide, 

 a smaller proportion of the silica, and the slight amoiint of sesquioxide of 

 manganese present, are in the form of colloidal hydroxides in the two red 

 soils ; 2) the rest of the alumina is mostly in the state of clay (kaolin,) 

 but also to a lesser extent in the form of silicates of aluminium, potassium 

 and sodium with and without iron and magnesium (micaceous minerals ?) ; 

 3) the excess of silica must be attributed to quartz ; 4) while the lime 

 in the two red soils is due almost exclusively to calcium carbonate, the 

 magnesia is only attributable in part to the carbonate of magnesium, the rest 

 belonging to silicates which are little soluble or insoluble in hydrochloric acid. 



In conclusion, the two red soils examined did not consist exclusively 

 of a clayey ochreous-quartzite matter as they also contained h^'droxide 

 of iron in the colloidal state, accompanied by geloltydrates of aluminium 

 and in smaller quantities, by silica and manganese. The two Sienna red 

 earths present a great analogy in this respect with those of Croatia, which 

 are considered similar to bauxites from the physical, mineralogical, and 

 genetic point of view. 



With regard to the genesis of the red earths in question, the Author 

 is inclined to consider them as deposits of colloidal solutions mixed with 

 matters originating from the alteration and weathering of anagenetic, schisto- 

 phylladic, quartzose, etc. rocks which in the " Montagnola " of Sienna ac- 

 company cavernous limestone, not excluding however the action of fer- 

 ruginous thermal waters slightly impregnated with manganese and charged 

 with carbonic acid gas. 



(i) vSee Vinassa de Regiiy P., " Red Soil ", Bulletin September itjis, pp. 1134-1138. {Ed.) 



