470 Extracts from the Proceedings of the British 



their plan for discussion before the Section, They described the 

 several methods adopted by MM. Boussingault and Ville, and 

 then illustrated by drawings their own methods and results. In 

 all cases the plants were growing in soil and atmosphere destitute 

 of all combined nitrogen in the first instance. To some, how" 

 ever, as their growth seemed to indicate the need, small and 

 known quantities of ammonia were added. Drawings of the pro- 

 gress of the plant showed an enormous increase of growth where 

 the ammoniacal supply was given. In these cases the plants 

 promised to yield seed, and their height and general development 

 vras pretty natural. In the other instances, owing to the com- 

 bined nitrogen of the*s.eed sown and the free nitrogen of the air 

 the plants were exceedingly small, and withered before coming to 

 perfection. The final result, however, could not be known until 

 the growing plants, the soil, and the pots in which they grew 

 were analysed, when the debtor and creditor account, so to speak, 

 of the nitrogen could be made up. Other researches were also in 

 progress to determine the relation of ;the gases evolved during the 

 growth of plants, to the constituents actually assimilated. 



Sectiok C. — Geology. 



General Sketch of the Districts already visited hy the Geologi- 

 cal Survey of India. By Thomas Oldham, A.M., F.R.S., G.S., 

 &c., Superintendent of Geological Survey of India. * 



The labours of the Geological Survey of India have been con- 

 ducted hitherto under great difiiculties. More recently, however, 

 the liberality of the Government of India had greatly extended the 

 establishment of the survey, and he trusted that their future pro- 

 gress. would be rapid and effective. The only general sketch-map 

 of the geology of India which they had was that published by the 

 late Mr. Greenough. This was a work of great value, and gave 

 abundant proof of the extent and labour of its author in its com- 

 pilation. As might be anticipated under the circumstances, it 

 was full of errors ; and perhaps few could speak more confidently 

 of this than himself. But at the same time it was a most valuable 

 contribution, and would prove a most useful guide to future ob- 

 servers. The ofiicer of the geological survey had examined seve- 

 ral districts of considerable area in detached positions, and the 

 results which he was able to lay before the section might there- 

 fore appear less connected than he could wish. But every day 

 would tend to unite them more closely ; and his object was now 



