HOT- WATER APPARATUS. 
37 
advantageous to employ one of the form figured as fig-. 3, No, 3. When the first 
bar supports all the cross bars, and there is no ring- to the g-rate, in this case the 
bars should only extend to within half an inch of the rim of the frame in which 
they revolve, to allow a draft close to the boiler surface. This form, however, is 
Fig. 3. No. 3. 
/ 
only recommended as an improvement, not having- 
been tried in practice. The following- proportions 
are recommended for the construction of boilers. 
The furnace in No. 1 may be conical, or nearly so ; 
the others would probably be, if made as repre- 
sented in Fig-. 1, a frustum of a cone, contracting- 
with a curved top to the required diameter of the 
upper aperture. Numbers 1 and 2 have only been 
tried, but the experience of those would recommend 
the adoption of the following- forms in further experiments. 
Upper diam. 
Lower diam. 
Height per- 
Thickness of 
Diam. of com. 
pipes union 
joints. 
Chimney 
of furnace. 
of do. 
pendicular. 
Boiler in water. 
diam . 
No. 1. 
6 in. 
9 in. 
18 in. 
H in. 
3 in. 
2_ 
do. 
10 
20 
H 
If 
n 
'•''2 
3*. 
do. 
12 
22 
3f 
4. 
do. 
14 
24 
2 
2 
4 
The proportions for No. 4 are g-iven on the same principle as the preceding ones ; 
but in all probability, where a power is required greater than that afforded by No. 3, 
it would be best to employ two boilers of the size of No. 2. The consumption of 
fuel would be less, and the fire more manageable, besides other indirect advantages : 
and it may be well to mention, that the proportions of one grate, boiler surface, and 
chimney in three boilers^, coincide very nearly with the proportions laid down by 
Mr. Tredgold. The only deviation is that which the peculiarity of their form 
renders necessary. 
No. 1 is probably the smallest size generally serviceable ; but a boiler rather 
less, whose lower diameter of furnace is eight inches, and communication pipe 
1 inch in diameter, attached to 36 feet of 2-inch pipe, in a well-glazed pit, and a re- 
servoir of 24 gallons, raises the temperature under 130 feet of glass, 19° Fahrenheit ; 
and maintains that temperature twelve hours with a loss of only 4°. It takes 
about three and a half hours of fire to get it up to its full work : but it begins 
to heat as soon as the fire is lighted. It requires looking at two or three times 
in the first three hours, and afterwards without attention will burn nearly all 
night. The whole quantity here heated is about 30 gallons ; and this apparatus 
would probably suffice amply for 200 or 250 feet of glass. 
No. 2 raised 40 gallons 50° per hour^ in open vessels, and in the open air ; 
and from a comparison of experiments made with it and the other boiler, it would 
appear to be nearly double its power. These data may suffice as some sort of 
guide for those who wish to apply the apparatus ; and it will probably be found 
that No. 3 has nearly double the power of No. 2. By employing coke instead of 
