24 Scientific Proceedings, Royal Dublin Society. 



following data :— shell = 2000 lbs. ; charge = 772 lbs. The ex- 

 treme range of these guns is about 10 to 12 miles Eng. Now, 

 as regards the height to which the ashes were shot up, we have 

 the following statement {Nature, vol. xxx. p. 13) : — " The steam 

 cloud, according to the measurements taken on board the German 

 man-of-war ' Elizabeth,' which left Anjar that morning at nine 

 o'clock, must have reached a height of at least 11,000 m. During 

 the much more violent explosion of Aug. 26th-27th the height, 

 if the above report may be relied on, may very well have attained 

 15 to 20 km." (that is from 9*3 Eng. miles to 12-4 Eng. miles)— 

 a height about equal to the extreme range of the 100 ton gun in 

 question, and without taking into account the increased range 

 which should be attained by a projectile shot vertically through 

 air of continuously decreasing density. 



Now, admitting that a comparison may be drawn between 

 the action of gunpowder in such a cannon, and that of the 

 gases or steam in the vent of a volcano, we have merely to 

 take the estimate of the quantity of ashes thrown up during 

 the Krakatoa eruption, and determine from that the corres- 

 ponding charge estimated as gunpowder. According to the re- 

 port in question, this quantity of ashes is given as 36 x 10 12 kg. ; 

 and as the charge in the case of the 100 ' ton gun is to the 

 projectile as / 7 2 , we may take as charge in the case of the 

 emitted ash, 36 x 10 12 x fffo - 36 x 10 12 x 0-386, or approxi- 

 mately 36 x 10 12 x 0-4 = 14-4 x 10 12 kg. powder. The table 

 gives the amount of gases generated per kg. of powder as 

 0*225 me. Therefore we have by the explosion of this supposed 

 charge of powder 14-4 x 10 12 x 0'225 mc. = 3'24 x 10 12 mc. at the 

 pressure 076mm. = 3,240,000,000,000 mc. 



To appreciate what this cube means relative to our atmo- 

 sphere, we may take this as having a height of about 5 miles, 

 or in kilometres, about 8 km. high : dividing, therefore, this 

 cube of gases by 8000 m., we have 405,000,000 kms. as the 

 surface which would be occupied by a volume of air of that 

 cube and 8 km. high : this would represent 405 kms., that is 

 a surface of about 20 km. x 20 km. = 12-2 miles x 12*2 miles. 

 But the height was really greater than 20 km., and has been 

 variously estimated at 40 to 50 miles = 64'4km. to 80 - 5 km. The 

 quantity of ashes was much greater than that calculated, while 



