309 



short, when vegetation has arrived at its proper period the crop is 

 found far beyond that of the same plants grov/n in pure air ; and, 

 v^eight for weight, they contain twice as much azote. Besides these 

 general effects there are others which are more variable, which de- 

 pend upon particular conditions, but which are equally worthy of 

 interest. In fact, by means of ammonia we can not only stimulate 

 vegetation, but, further, we can modify its course, delay the action 

 of certain functions, or enlarge the development and the modifica- 

 tion of certain organs. The author further remarks, that if its use 

 be ill- directed, it may cause accidents. Those which have occurred 

 in the course of his experiments appear to him to throw an unex- 

 pected light upon the mechanism of the nutrition of plants. They 

 have at least taught him at the expense of what care ammonia may 

 become an auxiliary of vegetation. These experiments, which were 

 made under the same conditions as those upon the absorption of 

 azote, are then described, and their numerical results given. 



To the conclusions already stated, the author adds that there are 

 periods to be selected for the employment of ammonia, during which 

 this gas produces different effects. If we commence its use when 

 several months intervene before the flowering season of the plants, 

 it produces no disturbance ; they follow the ordinary course of their 

 vegetation. If its use be commenced at the time of flowering, this 

 function is stopped or delayed. The plant covers itself with leaves, 

 and if the flowering takes place all the flowers are barren. 



3. " An Account of Meteorological Observations in four Balloon 

 Ascents made under the direction of the Kew Observatory Com- 

 mittee of the British Association." By John V/elsh, Esq. Com- 

 municated by Colonel Sabine, R.A,, Treas., V.P.R.S., President of 

 the British Association, on the part of the Council of the Association. 

 Received April 27th, 1853. 



The object contemplated by the Kew Committee in the balloon 

 ascents, of which an account is given in this communication, was 

 chiefly the investigation of the variations of temperature and humidity 

 due to elevation above the earth's surface. Specimens of the air at 

 different heights were also obtained for analysis. 



The instruments employed were the barometer, dry- and wet-bulb 

 hygrometer, and Regnault's condensing hygrometer. 



The barometer was a siphon, on Gay-Lussac's construction, with- 

 ' out verniers ; the upper branch of the siphon being alone observed, 

 corrections having been previously determined for inequality of the 

 tube at different heights of the mercury. 



Two pairs of dry and wet thermometers were used, one pair having 

 their bulbs protected from radiation by double conical shades open at 

 top and bottom for the circulation of the air, the surfaces being of 

 polished silver. The second pair were so arranged, that by means 

 of an " aspirator," a current of air was made to pass over the bulbs 

 more rapid than they would be exposed to by the mere vertical 

 motion of the balloon. The object of this arrangement was to 



