THE FARMER'S MAGAZINE. 



511 



monster firmly. Our old agricultural buildings would 

 be racked to pieces by steam-power. It would do far- 

 mers good to see the unerring movement of our manu- 

 facturing machinery, all smooth and steady. A well- 

 finished engine is almost as finished as the works of a 

 watch, and as far as possible should be kept free fiom 

 dust, grit, or rust. This is the case in our manufactur- 

 ing districts, where the engine has a room to itself, as 

 clean as a drawing-room. Farmers who use steam 

 ought to know something about it, and I would recom- 

 mend their adopting Messrs. Ransome's instructions, 

 ably given in the last number of the " Royal Agricul- 

 tural Society's Journal,^' which every farmer of 150 

 acres would find a profit in subscribing to. Mr. 

 Williams's plan tf avoiding smoke is worthy of in- 

 spection, and may be seen at Messrs. Redpath and Co.'s 

 foundry, near the Stepney station. A five-pound note 

 will save much waste and nuisance, and give increased 

 power. Mr. Fairbairn's test of safe boiler-pressures is 

 as follows: he says — "The following table, deduced 

 from my own experiments, exhibits the safe working- 

 pressure and the bursting-pressure of boilers of different 

 diameters, calculated for an external shell of a thickness 

 of fths of an inch : 



Taking from the above table the strength of a boiler 7 

 feet in diameter, we find its bursting pressure to be 

 SOSalbs. per square inch." There are certain practical 

 matters in relation to fixed engines which are worth 

 knowing. I therefore consulted the following boi-jks 

 with much advantage: " A.rmstrong on Boilers," 

 " Williams on Combustion ;" I have also " Dr. Albau 

 on High-pressure Steam," and " Craddock's Lectures 

 on the Steam-engine." This information and my own 

 observation have induced me to come to the following 

 practical conclusions upon certain points connected with 

 fixed steam-engines not multitubular : 



FuR.vACE. — That there should be one square foot of 

 fire-grate for every horse-power. That the fire-bars 

 should be at least two feet below the boiler-bottom. 

 That the space above the bridge should be equal in area 

 to thirty square inches for every foot of fire-grate. 

 That the flues in every part, and the opening into the 

 chimney, should have an area of thirty square inches 

 for every foot of fire-grate. That the furnace-plate 

 and fire-door should be pierced with thirty half-inch 

 holes for every foot of fire-grate, a deflecting-plate 

 being placed in the furnace- That the boiler should 

 Viave 9.% leeiat nifte feet oi ijeatlng eurfftce to ever foot of 



fire-grate. That there should be very little stoking, and 

 no smoking. That it would repay well to read Wye 

 Williams on Combustion, Dr. Alban on High-pressure, 

 and Armstrong on Boilers, all published by Weale, 

 High Holborn ; also Craddock's Chemistry of the 

 Steam-engine, by Simpkin and Marshall. That loco- 

 motive or multitubular boilers generate steam quickly, 

 but are difficult to clean, and soon wtar out. That 

 Cornish boilers are less safe for high-pressure than flue- 

 boilers, unless very carefully supplied with water ; but 

 if kept filled with water, and the steam taken from 

 another boiler or vessel attached to and above them, as 

 in Mr. Collinson Hall's plan, then I consider the 

 Cornish boiler perfectly safe and most economical. That 

 flue-boilers, having a length of three limes their dia. 

 meter, are simple, durable, aud safe. That we should 

 have Sylvester's trap-doors at each end of the centre and 

 every other flue, so as to cleanse them when required. 

 That rushing air, like rushing water, will travel quickest 

 through a smooth clean flue free from sharp angles or 

 rough obstructions. Mr. Fairbairn has recently dis- 

 covered that, in long thirty feet flue-boilers, the flue is 

 of only one-third the strength of the outside shell, al- 

 though of the same substance. His remedy is simple 

 and effective. This deficiency of flue strength does not 

 exist in boilers under ten feet in length. He says — " If 

 we take a boiler of the ordinary construction, thirty feet 

 long, and seven feet in diameter, with one or more flues, 

 three feet or three feet six inches in diameter, we find 

 that the cylindrical external shell is from three to four 

 times stronger in its powers of resistance to the force 

 tending to burst it, than the flues are to resist the same 

 force tending to collapse them. This being the case in 

 boilers of ordinary construction, it is not surprising that 

 so many fatal accidents sliould have occurred from the 

 collapse of the internal flues, followed immediately by 

 the explosion and rupture of the outer shell. To remedy 

 such evils, and to place the security of vessels so im- 

 portant to the community upon a more certain basis, it 

 is essential that every part should be of uniform strength 

 to resist the forces brought to bear upon it. The equali- 

 zation of the powers of resistance is the more important, 

 as the increased strength of the outer shell is absolutely 

 of no value, so long as the internal flues remain, as at 

 present, liable to be destroyed by collapse, at a pressure 

 of only one-third of that required to burst the envelope 

 which surrounds them." That feed-pumps should have 

 a vertical action, with a wide piston and short slow 

 stroke, experience having taught me the inconvenience 

 of a long thin piston and rapid horizontal motion. 

 Perreaux's vulcanized India-rubber valves are infallible. 

 That it is desirable to have a supply of water well- 

 heated by the waste steam passing around it before 

 pumping it into the boiler. That all bearings for 

 rapidly-revolving shafts should be very wide, so as to 

 diminish friction by pressure, and admit of lubrication. 

 That great care should be taken not to bind the shafting 

 by over- screwing the brasses. That all riggers should 

 be turned perfectly smooth, so as to make the driving 

 straps bind on them, by excluding air. That all bear- 

 ings nhouW b«5 well aupportcd and free from the ka»t 



