A. C, of Maiden, Mass., writes:

"I inclose you a diagram of boiler connected to range as at present. The boiler continually snaps and breaks the pipes. The boiler holds about 120 gallons and is raised as high as it is possible to get it. Can you make any suggestions to obviate the trouble, and what is the best thing to do to get the best results?"

[Judging from your diagram, your sole and sufficient cause of trouble is that the circulation is so sluggish that steam forms in the water-back and accumulates there until it comes in contact with the colder water in the boiler, when it is suddenly condensed, causing a violent water hammer, and break, ing the pipes as you describe. The remedy is to raise the flow pipe from the water-back to the boiler, so as to enter the boiler some distance above the water-back as shown by the dotted lines at A, and the higher the point at which the flow pipe enters the boiler the more rapid and efficient will be the circulation, though usually a difference of elevation of 2 feet or so will give sufficient circulation to heat the water rapidly and prevent it from remaining long enough in the water-back to be turned into steam.

The only efficient cause of the circulation between a water-back and boiler lies in the fact that there is a column of water in the flow pipe and water-back which is hotter than that at a corresponding elevation in the boiler. The higher this column, and the greater the difference of temperature, the more rapid the circulation will be. It is the rise of the flow pipe, not its length, that does the work, and the direction taken by the lower pipe leading from the boiler to the water-back has no effect on the circulation whatever. It must be remembered, however, that while increasing the height of the flow pipe tends to accelerate the circulation, it cannot effectually overcome the resistance offered by too many bends or fittings, or too small size of pipe, or, perhaps, some obstacle that has lodged in it, so that if after raising the flow pipe the circulation is still unsatisfactory, you may be sure that some obstruction such as above mentioned exists in the pipes, and if carefully sought for and removed there will be no further trouble. In this connection you will do well to read carefully the answer given in our issue of March 16, 1889, to the question " How to connect a water-back."]