Notes on Steam Boilers. 325 
more clearly how the concentrated steam generated on 
high tubes throws up the water thus causing the 
wasteful priming. 
In passing, one connedted with sugar manufafture 
cannot help but see the advisability of boiling vacuum 
pans as seldom as possible with the liquor in the top 
part, and thus avoid the priming which is not at all 
uncommon in some pans. Figures 5 and 6, illustrate this 
as seen through the sight glass. The vacuum pan with 
its sight glasses is most instructive in the cause of 
priming ; in it the velocity is very high, on account of 
the immense specific volume of the steam at 13 lbs, 
vacuum. The boiling is consequently very violent and 
the priming is so great, that savealls are necessary equip- 
ment of pans — indeed, no longer since than last week, my 
attention was drawn to a saveall that was completely 
filled with small grain sugar, accumulated by the high 
velocity of the steam which is about 2\ feet per second. 
It is the excessive priming that causes so much wasted 
sweets in the condensed water from the vacuum pumps, 
and I believe few of us attach sufficient importance to it. 
It is from the foregoing reasons also that we require 
more attention to be given to the circulation of the 
liquor, and separation of the steam from the liquor in 
Triple Effets, where the depth of dense priming often 
exceeds 6 feet. 
I think I cannot do better than give you Mr. LAVING- 
TON E. FLETCHER'S opinion on priming in these boilers, 
as expressed to me in a letter last month. " No doubt 
the fa6l that the water with which your boilers are fed, is 
slimy and contains vegetable matter, has much to do with 
the priming ; and the harder you fire the boilers the 
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