72 Book of Locomotives 



For two years Mr. Ivatt watched his 

 experimental engine and then rinding it had 

 more than justified itself, he built ten 

 similar machines. A further ten brought 

 the class up to twenty-one, and it was seen 

 that the locomotive problem was solved on 

 the Great Northern for some years. 



Unfortunately, the coming of the " Atlan- 

 tic " meant the doom of the " single " and 

 as each new monster appeared it was certain 

 that one of the eight-footers would reach 

 her long home. 



Still the loads went on growing, but Mr. 

 Ivatt did not find it necessary to alter his 

 type all that was wanted was a larger 

 boiler. 



In the " 251 " class an ample boiler was 

 provided, but even with the greater boiler, 

 the cylinder dimensions of the " 990 " class 

 were slightly reduced. The new boilers 

 were 16 feet 2 inches with a girth of 5 J feet. 

 An immense heating surface is provided 

 with the wide fire-box and numerous tubes, 

 totalling in all 2,500 square feet whilst a 

 steam pressure of 175 Ib. is used. 



