1862.] 29 



I beg, finally, to sum up briefly the conclusions which appear to 

 me to be deducible from these experiments. 



1st. That the experiments with the model mortar, by giving the 

 longest range and the shortest that are due to certain positions of the 

 centre of gravity in a vertical plane in positions the reverse of those 

 obtaining in large guns, while the other positions remain the same, 

 as to their effect on the range, as in large guns, appear to render 

 admissible the view that the causes of lateral and vertical deviations, 

 which have hitherto mostly been assumed to be similar, may not be so. 



2ndly. That from the above experiment it also results that there 

 must be a length and calibre in which the range will be the same, 

 whether the centre of gravity of an eccentric spherical projectile be 

 placed above or below, while in the same gun all the other deviations 

 due to the other positions will be similar to those obtaining in both 

 large guns and small models. 



3rdly. It appears (at least with the dimensions of gun and pro- 

 jectile here experimented with) that there is no decided rotation in 

 any of the four positions in a vertical plane, excepting that of centre 

 of gravity " above " the geometrical centre ; and it may perhaps be 

 fairly assumed that in the positions in which disks do not rotate, 

 spheres (at all events, of like dimensions) cannot. 



4thly. That if the results of these experiments with the model 

 disk -gun may be viewed as indicative of similar results from large 

 guns, then the above-mentioned phenomenon of rotation in one posi- 

 tion only renders doubtful the previous conclusions on the direction 

 of rotation, which have been based on a view of the rotation not 

 being thus limited to one position. 



5thly. It appears that to rotate outside the gun, it is requisite 

 that the disk (and probably sphere also) must be free to rotate 

 within it. 



6thly. That rotation may be imparted sufficient to be permanent 

 on one axis, but not in one plane a matter of no consequence at 

 close quarters ; while, by certain means, rotation may approximately 

 be secured in one plane when the projection has been in a vertical 

 plane ; this has been seen at least up to thirty yards at a target, and 

 longer distances not yet tried at a target ; but much within the 

 above distance the other phenomena are seen to occur ; and it may 

 be assumed that if a disk will keep upright through several inches 



