1817.] Escape of Gases through Capillary Tubes. 5 



where the pressure is comparatively small; but the Tuscan 

 laguna offers the only instance in which the action of these 

 fires extends, or has extended, to the surface at which the 

 water collected in the mountains finds its way to the sea, so as 

 to enable it to dissolve caustic calcareous matter. 



On the Escape of Gases through Capillary Tubes*. 



As the mobility of a body, or the ease with which its particles 

 move among themselves, depends entirely upon its physical 

 properties, little delay would arise in the mind, on a consider- 

 ation of the probable comparative mobilities of the different 

 gases. These bodies being nearly similar in all the physical 

 properties, except specific gravity, which can interfere with 

 internal motions generated in them, would be supposed to 

 have those motions retarded in proportion as this latter cha- 

 racter increased ; but as this supposition has not been di- 

 stinctly verified, the following experiments, though possessed 

 of no peculiar claim to attention, may deserve to be recorded. 

 The apparatus was a copper vessel of the capacity of 100 

 cubic inches nearly, to which a condensing gauge was attached. 

 Four atmospheres of the gas to be tried were thrown into it, 

 and then a fine thermometer tube, 20 inches in length, was 

 fixed on by adjusting pieces : the gas was suffered to escape 

 until reduced to an atmosphere and a quarter, and the time 

 noticed by a seconds' pendulum. In this way, 



Carbonic acid gas required 156*5 minutes to escape. 

 Olefiant gas 135'5 



Carbonic oxide ,, 133 ,, 



Common air ,, 128 ,, ,, 



Coal-gas 100 



Hydrogen 57 



These experiments tend to show, that the mobility of the 

 gases tried decreases as their specific gravity increases, and 

 they are corroborated by others made with vanes. A wheel, 

 having small planes attached to it, as radii perpendicular to 

 the plane of motion, was made to rotate by a constant force in 

 atmospheres of different gases, and the times which the motion 



* Quarterly Journal of Science, iii. 354. 



