Volume 30, Issue 2
August 1949, pages 61-119
pp 61-68 August 1949
A technique for the breeding of standardCulex fatigans for toxicological studies as well as a method for the evaluation of toxicity are described. Experiments have shown that successive generations of the test insects show progressive resistance to a contact insecticide. The progressive resistance to DDT over a ten-month period is recorded.
pp 69-94 August 1949
—Sir Thomas Holland proposed the termSivamalai Series to include a group of alkaline rocks which are prevalent in the neighbourhood of Sivamalai in the Coimbatore District. Since the publication of Holland’s Memoir little attention has been paid to them. As a result of detailed petrographic study of the rock types of this area a geological map has been prepared by the present writer (see map appended). Three types of rocks and a rose coloured variety of nepheline have been analysed.
The rock suite is characterised by soda-rich feldspars and pyroxenes, the feldspars being mostly varieties of crypto and microperthite, of the exsolution and replacement types. The plagioclase feldspars in these rocks have 13–18% ‘An’ content and invariably exhibit the Albite-Ala twin law. The rose-coloured nepheline was found to be particularly rich in soda and having low indices of refraction. The pyroxene in the pyroxene syenites is pleochroic ægirine-augite, occurring intimately associated with olivine and hypersthene. Three varieties of amphibole were noticed in these rocks, one of which is similar to ‘Girnarite’, a species named by Mathur.
Eight distinct types of rocks have been recognised on the basis of detailed petrographie examination, these being (1) coarse nepheline syenite, (2) aplitesyenite, (3) biotite-nepheline-syenite, (4) hornblende-nepheline-syenite, (5) hornblende-nepheline-syenodiorite, (6) even-grained granulitic nepheline-syenite, (7) ægerine-augite-syenite, and (8) microperthitite.
Rock types 3, 5 and 7 have been analysed and these together with an analysis given by Holland have been plotted on the ‘QLM’ and ‘πκ’ triangular diagrams after Niggli. These diagrams bring out the undersaturated nature of these rocks and their affinity to the Atlantic Suite. Field evidence suggests a syntectic origin for these rocks, but for a fuller understanding of the genesis of the suite it will be necessary to undertake more extensive chemical studies.
pp 95-98 August 1949
pp 99-119 August 1949
Under the highly humid conditions prevailing in Eastern India during the monsoon, storage of gur at this time of the year presents a serious problem as the material is apt to suffer greatly in quality as well as quantity on account of moisture absorption, resulting in inversion and fermentation which gives rise to great deterioration and loss. The country methods of storage in vogue (e.g., inside a blanket of bhusa or wheat straw) gives far from satisfactory results and in these days of acute food shortage the need for evolving an effective storage method must be regarded as a national one, In these investigations, furnace ash and charcoal powder (selected respectively on account of their hygroscopic and adsorptive properties) have been examined with respect to their efficacy as storage blankets against the com-@#@ monlyused storage material, wheat bhusa as also storage under exposed conditions.
The experiments bring out the unique performance of furnace ash (from gur furnace) in affording perfect protection from moisture and saving gur under storage from the least deterioration during the rains. The reason for this behaviour obviously lies in the highly hygroscopic nature of ash, by virtue of which property, the material arrests the atmospheric moisture in itself, thus preventing it from reaching the gur stored inside. The utility of furnace ash as storage blanket has been discussed from different standpoints.
Experiments on changes in important physical and chemical attributes of gur under different conditions of storage reveal interesting differences in behaviour which lead to definite characteristics in respect of these properties, associated with different stages of deterioration in storage. These are stated here in brief.