226 Lieut.-Col. Emmettcw the Carbonic Acid in the Atmosphere. 



the remaining lime-water; consequently left 80 for the carbonic 

 acid in the air*. 



Experiment 2. 25th of Sept. Receiver and acid as before, 

 but the lime-waters but 210 for neutralization. Wind strong 

 from S. W. ; thermometer 80°. 



Sept. 28th. The lime-waters from the receivers took 120 

 grain measures for neutralization, leaving 90 for carbonic 

 acid gas ; a very nearly similar result as before. 



Experiment 3. Oct. 2nd, at 5 p.m. ; wind S. W. at the 

 cessation of a heavy gale, with much rain ; therm. 78°, barom. 

 30*00. 



Receiver and acid as before. Lime-water required 390 mea- 

 sures for neutralization. Tested that in receivers at 5 p.m. of 

 the 8th inst. ; therm. 75°. This required 210 measures of 

 the acid for neutralization, leaving 180 for carbonic acid, being 

 double that before, or about 1 in 3920. 



Experiment 4. Oct. 11th, 4J p.m. Collected air as be- 

 fore. There had been much rain during the day, but it was 

 fine and calm after 3 p.m. Therm. 77°^. In this case the 

 lime-water took 375 measures for neutralization. 



Tested that in the receivers on the 18th ; therm. 75°. The 

 1500 grains in the receiver required 280 grains for neutrali- 

 zation, leaving 95 for carbonic acid gas. 



In the experiments 1, 2, and 4, the gas is consequently about 

 1 in 8000 ; and in the 3rd, 2 parts in 8000. In the 3rd, the 

 receiver was out during the rain, but so placed as to prevent 

 its entrance. The air in 2 and 4 had traversed the small island 

 of St. Davids, distant perhaps \\ of a mile, thinly in habited, 

 and thence the inlet of the sea, St. George's Harbour. 



The acid was pure, brought out with me for particular ex- 

 periments. 



Looking to the general result, and in No. 3 the quantity 

 being double, inaccuracy of observation of the measures might 

 possibly have led to the differences. 



[Probably the whole terraqueous globe is enveloped with 

 the same atmosphere, as is the case in azotic and oxygenous 

 gases. The reason why the carbonic acid is not so obvious, 

 is its extreme minuteness. The whole quantity is not more 

 than j-qjs-q th part of the mass, or TJ ^ part of the volume of 

 the atmosphere. I have examined the air in a hothouse in 

 July, with the air pent up during the night, and open in the 



* The receiver was not long enough exposed : my bottle was two gal- 

 lons ; it was exposed three or four days, and agitated to exhaust the air. 

 Consequently ten times as much would probably be required by ten timet 

 the size of the bottle. 



