W. Crookes on the Wax-paper Photographic Process. 159 



the bore, and was covered but £ inch deep with powder — the 

 orifice facing toward the muzzle of the gun. The momentum 

 of the gases rushing forward in the explosion seems to have re- 

 lieved the instrument from a part of the pressure sustained by 

 the sides of the bore at the same distance from the bottom. 



The variations of pressure sustained by the gun when fired 

 with charges very nearly the same, are greater, as might be ex- 

 pected, than the variations of initial velocity imparted to the 

 ball under similar circumstances. When the combustion of the 

 powder takes place with more than average rapidity the pres- 

 sure in the first instants of the explosion is augmented, but its 

 action on the ball is not so well sustained as in the case in 

 which the combustion is more slow and consequently longer 

 continued. 



The following table of initial velocities of 6 pdr. balls, extracted 

 from a table in Major Mordecai's " Second Eeport" of his ex- 

 periments on gunpowder, will serve for the comparison. 



Initial velocities of balls fired from a 6 pdr. gun. 



Weight, 

 lbs. 

 1-5 

 15 

 15 

 1 5 

 1-5 

 IS 



Jer. 



Shot. 



Tmtial 

 Velocity. 



Height. 



We ght. 



Dinm. 



in. 



lbs. 



in. 



ft.pr.sec'd. 



48 



6'11 



358 



1594 



4-8 



6-15 





1580 



49 



613 



(C 



1553 





6 26 



« ' 



1538 





6 37 





1 98 





63 



tt 



1520 



Fixed am- 

 munition. 



Art. XIII. — Description of the Wax-paper process employed for 

 the Photo- Meteor ographic Registrations at the Radcliffe Observa- 

 tory ; by William Crookes, Esq.* 



1. Before attempting to select from the numerous Photo- 

 graphic processes, the one best adapted to the requirements of 

 Meteorology, it was necessary to take into consideration a num- 

 ber of circumstances, comparatively unimportant in ordinary 

 operations. 



To be of any value, the records must go on unceasingly and 

 continuously : 



1st. Therefore, the process adopted must be one combining 

 sharpness of definition, with extreme sensitiveness, in order to 

 mark accurately the minute and oftentimes sudden variations of 

 the instruments. 



* From the Astronomical and Meteorological Observations made at the Radcliffe 

 Observatory, Oxford, in the year 1854, under the superintendence of Manuel J. 

 Johnson, M.A., Radcliffe Observer. Vol. XV. Oxford: 1856. 



