The machine, which is made steam-tight, is partially filled with water, and placed on a fire stove. It is evident that a comparatively small quantity of fuel will generate sufficient steam to heat a large surface, especially if the smoke flue is placed under the whole length of the machine.
As it is impossible to fire-burn the Tea, dried by the steam-heated Dryer, the enormous advantage of being independent of the care and judgment of coolies, and of the necessity of uninterrupted European supervision, is too evident to require comment.
Then comes the figure of the Dryer with the following note:--
“Barbacue-shaped Tea Dryer.--The far end should be slightly higher than that over the fire, to allow the space over it to be full of water.
An apparatus for escape of steam and supplying water is inserted in the end plate covering the boiler.”
The _Ceylon Observer_, referring to the above, asks the following questions:--
Is it really impossible by means of steam to over-heat, though we may not, indeed cannot, “fire-burn” Tea? And when a boiler is employed to generate steam, do we become quite independent of the care and judgment of coolies, and avoid the necessity of uninterrupted European supervision? Will not a thermometer be necessary to indicate the proper degree of heat, will it not require close watching, and will there not be danger of the boiler exploding if neglected? The danger may be reduced to a minimum, but we should be glad of proof that it cannot exist.
Mr. Shand in reply writes--With reference to your remarks and queries regarding my Tea-drying machine, will you allow me to mention that, as it is not intended to sustain any pressure of steam, the drying surface cannot easily be heated over 150 degrees.
As a matter of course, the Tea takes a longer time to dry than when made by Siroccos, in which the temperature is maintained at 275 degrees, but the extent of drying surface available makes this a matter of secondary importance.
I did not mean that no care or attention is required to keep up fire and supply boiling water periodically from a cistern placed over the flue; but you can understand that the same care, judgment and observation is not required to dry Tea at a comparatively low temperature as at a very high one: for instance, it does not injure coffee to allow it to remain on the barbacue after it is thoroughly dry; but put it in a roaster, and what care and judgment is not required to perfect the roasting!