72 EEPORT— 1888. 



Exfevsion. — The specimens 2 to 7 have an extension which, thouo'hi 

 sh'ghtly lower than usual, still accords with what would be inferred from 

 the elastic limit and breaking load. If silicon has exerted any influence 

 in these specimens, it is not well marked, though the low extension may 

 be partly due to this cause. With more silicon the extension is distinctly 

 reduced. 



Eedudion of Area. — This follows mucb in the same order as the exten- 

 sion, and is distinctly lowered with the higher proportions of silicon. 



These results may be summarised as follows : — 



On adding silicon in proportions not exceeding 0"5 per cent, to ingot 

 iron containing manganese, the metal rolls well, and does not show any 

 signs of red-shortness ; it welds perfectly with all proportions of silicon, 

 and (with the somewhat doubtful exception containing 0-5 per cent.) is 

 not brittle when cold. With less than about 0-15 per cent, of silicon the 

 limit of elasticity, the breaking load, the extension, and reduction of area, 

 are but little, if at all, appreciably affected by the presence of silicon, but 

 with more than O'lS per cent, of silicon the limit of elasticity and break- 

 ing load are increased, while the extension and reduction of area are 

 distinctly decreased by the presence of silicon. The effect exerted by 

 silicon in increasing the tenacity of ingot iron is not nearly so great as 

 that of carbon. The relative hardness is very slightly affected by the 

 proportions of silicon used in these experiments. 



It is to be regretted that, largely on account of the outlay it would 

 have involved, these experiments have been conducted on a comparatively 

 small scale, the ingots used weighing only about 40 lbs. On this account it 

 has not been tbund practicable to perform tests connected with resistance 

 to shock, a point to which the attention of the Committee has been several 

 times directed, and which is, from a practical point of view, of consider- 

 able interest.' 



Third Rejjort of the Committee, consisting of General J. T. 

 Walker, Sir William Thomson, Sir J. H. Lefroy, General 

 E. Strachey, Professors A. S. Hersceel, G. Chrystal, 

 C. NivEN, J. H. PoYNTiNG {Secretary), and A. Schuster^ 

 aoid jNIr. C. V. Boys, appointed for the ptcrpose of inviting 

 designs for a good Difereniinl Gravity Meter in supersession 

 of the pjendulum, whereby satisfactory restdts may he obtained 

 at each station of observation in a feiu hours instead of the 

 many days over tvhich it is necessary to extend penduluv% 

 observations. 



Mk. Boys has not yet been able to construct the instrument referred 

 to in the last report. Meanwhile no new design has been received. 



The Committee ask for reappointment and a renewal of the grant of 

 lOZ. made last year. 



' A more complete account of the above experiments is in type, and will be 

 published in the Journal of the Chemical Society. 



