511 



explaining the manner of conducting them and stating the detailed 

 results, would be rather lengthened, and would require drawings 

 and diagrams, for all of which I have carefully preserved the requi- 

 site data ; but before proceeding to put these in form suitable to be 

 submitted to the Royal Society, I am desirous of prosecuting the 

 remainder of the very interesting and important experiments which 

 have been entrusted to me, that portion of the whole, namely, 

 which relates especially to centrifugal pumps. I have also to state, 

 that if my engagements permit, I should be desirous of proceeding 

 with a renewed and more extended set of experiments on the fric- 

 tion of discs, with an apparatus depending on the same leading 

 principle as that which I have already used, a principle which on 

 trial has been found remarkably well suited for the desired purpose. 

 For the attainment of greater accuracy and of a wider range of the 

 experiments, it seems to me that no better method of procedure 

 could be adopted, than to follow the same leading principles, with 

 an apparatus of rather more refined construction, involving such 

 improvements in details as have been suggested by the experience 

 gained in the course of the experiments already made, and for the 

 sake of greater steadiness of motion, worked by steam power instead 

 of the hand of an operator. Should I have it in my power to con- 

 duct this renewed set of experiments, a detailed account of them 

 will be preferable to a detailed account of those already made. 



In respect to the experiments on Centrifugal Pumps, I have to 

 say that I have prepared plans for an experimental apparatus on 

 principles which 1 consider are peculiarly well suited for the attain- 

 ment of useful aud accurate results, and that I intend to proceed 

 with the experiments as soon as my engagements shall permit. 



I have further to state, that from the Experimental Fund of 50 

 granted by the Royal Society, the entire outlay as yet incurred has 

 been 6 5s. 9d , leaving a balance of 43 14*. 3d. for the more 

 extended experiments yet remaining to be made. 



JAMES THOMSON. 

 Belfast, April 13, 1855. 



