336 
to Captain Boxer, Superintendent of the Laboratory Department, Wool- 
wich, and to General Portlock, at that time Commandant of the Royal 
Military Academy. The design, as may be seen, shows the whole chase 
of the mortar, constructed in plies of two thicknesses of superimposed 
rings, arranged conically, so as to admit of producing the initial tension 
either by driving on, or by shrinking on hot, and the cast-iron chamber, 
hooped externally with wrought iron. This, then, is the date of my 
first publication of this method of construction—seven months prior to the 
earliest date assignable to Captain Blakely’s first publication im print, and 
nearly six months before he produced lus first experimental gun. 
The 36-inch mortars were ordered by Government to be constructed 
early in April, 1855, and I had my designs and specifications for them 
in the contractor’s hands, and the work in progress, on the 11th of June, 
1855. Speed in their completion was at that time primary to all other 
considerations to bring them before Sebastopol and Sweaborg; and with 
that view, having found that contractors were ready to undertake to 
forge the chases in a single thickness, I abandoned the more tedious con- 
struction in superimposed rings. Within a short time, however, the 
bankruptcy of the contractor (Mare, of Blackwall), and the sudden peace 
with Russia, afforded an opportunity for goimg back to the original prin- 
ciple of construction, and so these two great mortars have been con- 
structed in rings, superimposed with initial tension, as in principle in 
the first instance designed. 
Early in May, 1855, I, for the first time, visited, in company with 
Professor Downing, and conversed on the subject of ordnance construc- 
tion, with Dr. Hart. On that occasion I stated to him my views of the 
increase of strength that might be attained by external hoops, and illus- 
trated to him my conviction that these would be more effective, as they 
were removed further from the axis, by reference to the hoop upon a 
common tub (as stated by me in discussion here on the 14th of May last, 
and on that occasion admitted by Dr. Hart, as still in his remembrance). 
My illustration was, that if you take off a hoop from a common tub, 
interpose a number of blocks between it and the exterior of the staves 
(or, what is the same thing, thicken the latter, the internal diameter 
remaining the same), and drive on the now lengthened hoop over the 
blocks with the same tightness, i.e., with the same strain per unit of 
section that it had before, then the tub will be able to bear a greater 
internal fiuid pressure than before. 
This involves the whole principle in question, and J am glad to find 
that the circumstance is still fresh in Dr. Hart’s memory, as sufficiently 
proving that, previous to my very first interview with him, both the 
method and the importance of the method, of ringed structure with ini- 
tial strain were generally known to me. Of that portion of our conver- 
sation to which Dr. Hart recurred here on the 14th of May last, 
namely, ‘that I referred him to a mechanical question, which I repre- 
sented as an application of the principle of the lever to a cylinder, by 
surrounding it with a series of blocks, and fastening a hoop round these 
blocks,” he has retained a less accurate recollection as to what took 
