4 tiMEHRI. 



at that time often pointing out that the internal econo- 

 mies of film evaporation would not admit of economies 

 not already obtained in other good and much simpler 

 evaporators. The same remarks hold good with regard 

 to the vexed but simple question of the economy of film 

 and water tube boilers, versus boilers of the ordinary 

 type. 



Other cases that are legion might be instanced to 

 show that so long as we conform with Carnot'S law 

 and RlLLIEUX's cycle, the evaporation per square foot of 

 heating surface is in no way conne6ted with fuel economy, 

 and that until some one introduces a more perte6l cycle, 

 the ground left unturned for us to cultivate and improve, 

 is very small indeed. 



With regard to the second paragraph, we all recognise 

 that invariably a deleterious aflive corroding gas is given 

 off; to carry this away in the old evaporators separate 

 pipes often conne6\ed the top of the calandrias to the 

 calandria pump pipes; this in all cases under observation 

 has proved useless ; the far better plan is that instanced 

 by Mr. CORNISH, viz., conne6ling the tops of the calan- 

 drias dire6l with the main pump. However, unless this is 

 done in a manner to get the condensed gas well diluted 

 with the injeftion water, the pumps are soon damaged; 

 the Vvriter well remembers a case where by attending to 

 these fa6ls the main triple pumps, instead of wearing out 

 after incessant trouble every three years, now give no 

 trouble whatever and show but little wear. Also another 

 case where by designing a pump with no internal bolts, 

 having a combined air vessel and receiver containing 

 lime for the calandria water to pass through, no trouble 

 has been experienced this last six years. The other day 



