PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 493 



about a quarter of an inch in diameter, and afterward enlarged to some 

 three inches. It is very encouraging now to hear we have made one nearly 

 two feet in diameter. 



Mr. J. Johnson. — At the last meeting enquiry was made as to what were 

 the component parts of common pottery? I have since found that in a 

 tube thirty inches long that there was four per cent, of flint, one and three- 

 quarters of China clay, and one per cent, of feldspar; so it will be seen 

 that it contains a large percentage of silex. 



Delano's improvement in stoves, exhibited at the last meeting, was, on 

 motion, referred to a select committee for examination. 



The subject for the regular discussion was then taken up. 



Iron- CLAD Vessels of War. 



Mr. J. L. Jones. — In connection with this subject I have the honor to state 

 a few facts, and ofier some remarks. I feel my inability to discuss this 

 subject before such an intelligent audience as this. I am but a youth, 

 scientifically speaking, but I hope you will elucidate this subject in a more 

 scientific manner than I am competent to do. I will endeavor to give you 

 my views on this subject, and then call your attention to some facts con- 

 nected with it. Nothing perhaps has been more clearly demonstrated, by 

 the results of experience, than the necessity of providing some mode of 

 rendering vessels of war impenetrable to heavy shots, and the effects of 

 concussion, without incurring the necessity of loading them down with iron 

 plates (or iron and wood combined), of such thickness and weight as to de- 

 stroy the sea-going qualities of the vessel and endanger its safety when 

 meeting a storm or heavy gale at sea. 



To effectually incorporate all these principles or powers, I will say that 

 I have great reason to believe the invention proposed by Commodore W. 

 D. Porter and myself, has been demonstrated to be the best ever tried in 

 modern times. 



We propose, in our invention, to employ a series of plates of iron or steel 

 alternately arranged with plates of vulcanized India rubber, or other elastic 

 substance. I propose to apply it to the sides of a vessel in alternate lay- 

 ers, fastened with bolts, as represented in the drawings. These bolts are 

 provided with elastic washers to prevent the nuts from being stripped off 

 by the reaction which takes place after being compressed by the force of a 

 cannon ball. 



With reference to the pattern or proposed mode of rolling the plates, and 

 the advantages to be derived from making them with ribs, forming grooves 

 in the centre, and with ribs on each edge, I wish to remark that it will 

 impart great rigidity to the plates, and assist in forming a continuous con- 

 nection, and will enable constructors to impart the requisite rigidity to a 

 vessel with less material than any other plan proposed. It also prevents 

 the undulations of the vessel from cutting off rivets and bolts, and when 

 used as planking for the hulls of vessels, with elastic cushions as repre- 

 sented iu the drawings, will effectually prevent leakage. Bolts with nuts 

 can be arranged so as to be adjusted at pleasure from the inside. We have 

 never proposed (as some at first thought) to resist the impetus of a cannon 

 ball with elastic substances alone, or by plating it on the outside of plate 



