326 TlMEHRI. 
more they will prime. Although we are not advocates of 
putting grease in the boilers, in your case no doubt a little 
grease would tend to reduce the priming. You allude 
to the scantiness of your steam space above the tubes. 
No doubt the more steam space, the less priming. Were 
your boilers 7ft. or 7ft. 6 inches diameter instead of 6ft. 
6 inches as at present, with the same amount of work to 
do, they would work more easily, and prime less. The 
large horizontal steam trunk you show, I should think 
a good arrangement for the prevention of priming. 
Our practice is to adopt anti-priming pipes : we 
generally make their length equal to the diameter of the 
boiler, but the longer they are the better. The aggregate 
area of the perforations should only slightly exceed the 
thoroughfare through the stop valve; I doubt if they 
would do better than the steam trunk with your slimy 
water." 
With a chimney draught, the ratio of the diameter of 
the tubes to their length should not exceed 1.28, otherwise 
the draught is not sufficient to keep them clean of soot, 
a very common fault with the long boilers in use here. 
It is very desirable to have a standard size and thus 
reduce the stock of tubes now obliged to be kept in the 
colony, and 4.5 internal diameter is perhaps as large as 
economy admits : this of course gives us a boiler 10 feet 
long. 
The long boilers most extensively adopted in England, 
however, are those known as the " Lancashire," and 
11 Cornish," and although objeftions to their use, on many 
grounds i have been raised from time to time, their 
popularity has in no way abated. They have fulfilled 
hitherto the general requirements of steam users ; they are 
