ESSAYS-1 [113]
are intimately connected with those which relate to the form proper to be given to the Fire-place itself, we must consider them all together.
That these inquiries may be pursued with due method, and that the conclusions drawn from them may be clear and satisfactory, it will be necessary to consider, first, what the objects are which ought principally to be had in view in the construction of a Fire-place; and secondly, to see how these objects can best be attained.
Now the design of a Chimney Fire being simply to warm a room, it is necessary, first of all, to contrive matters so that the room shall be actually warmed; secondly, that it be warmed with the smallest expence of fuel possible; and, thirdly, that in warming it, the air of the room be preserved perfectly pure, and fit for respiration, and free from smoke and all disagreeable smells.
In order to take measures with certainty for warming a room by means of an open Chimney Fire, it will be necessary to consider HOW, or in WHAT MANNER, such a Fire communicates heat to a room. This question may perhaps, at the first view of it, appear to be superfluous and trifling, but a more careful examination of the matter will show it to be highly deserving of the most attentive investigation.
To determine in what manner a room is heated by an open Chimney Fire, it will be necessary first of all to find out, UNDER WHAT FORM the heat generated in the combustion of the fuel exists, and then to see how it is communicated to those bodies which are heated by it.
In regard to the first of these subjects of inquiry, it is quite certain that the heat which is generated in the combustion of the fuel exists under TWO perfectly distinct and very different forms. One part of it is COMBINED with the smoke, vapour, and heated air which rise from the burning fuel, and goes off with them into the upper regions of the atmosphere; while the other part, which appears to be UNCOMBINED, or, as some ingenious philosophers have supposed, combined only with light, is sent off from the fire in rays in all possible directions.
With respect to the second subject of inquiry; namely, how this heat, existing under these two different forms, is communicated to other bodies; it is highly probable that the combined heat can only be communicated to other bodies by ACTUAL CONTACT with the body with which it is combined; and with regard to the rays which are sent off by burning fuel, it is certain that THEY communicate or generate heat only WHEN and WHERE they are stopped or absorbed. In passing through air, which is transparent, they certainly do not communicate any heat to it; and it seems highly probable that they do not communicate heat to solid bodies by which they are reflected.
In these respects they seem to bear a great resemblance to the solar rays. But in order not to distract the attention of my reader, or carry him too far away from the subject more immediately under consideration, I must not enter too deeply into these inquiries respecting the nature and properties of what has been called RADIANT HEAT. It is certainly a most curious subject of philosophical investigation, but more time would be required to do it justice than we now have to spare. We must therefore content ourselves with such a partial examination of it as will be sufficient for our present purpose.
A question which naturally presents itself here is. What proportion does the radiant heat bear to the combined heat?--Though that point has not yet been determined with any considerable degree of precision, it is, however, quite certain, that the quantity of heat which goes off combined with the smoke, vapour, and heated air is much more considerable, perhaps three of four times greater at least, than that which is sent off from the fire in rays.--And yet, small as the quantity is of this radiant heat, it is the only part of the heat generated in the combustion of fuel burnt in an open Fire-place which is ever employed, or which can ever be employed, in heating a room.
The whole of the combined heat escapes by
That these inquiries may be pursued with due method, and that the conclusions drawn from them may be clear and satisfactory, it will be necessary to consider, first, what the objects are which ought principally to be had in view in the construction of a Fire-place; and secondly, to see how these objects can best be attained.
Now the design of a Chimney Fire being simply to warm a room, it is necessary, first of all, to contrive matters so that the room shall be actually warmed; secondly, that it be warmed with the smallest expence of fuel possible; and, thirdly, that in warming it, the air of the room be preserved perfectly pure, and fit for respiration, and free from smoke and all disagreeable smells.
In order to take measures with certainty for warming a room by means of an open Chimney Fire, it will be necessary to consider HOW, or in WHAT MANNER, such a Fire communicates heat to a room. This question may perhaps, at the first view of it, appear to be superfluous and trifling, but a more careful examination of the matter will show it to be highly deserving of the most attentive investigation.
To determine in what manner a room is heated by an open Chimney Fire, it will be necessary first of all to find out, UNDER WHAT FORM the heat generated in the combustion of the fuel exists, and then to see how it is communicated to those bodies which are heated by it.
In regard to the first of these subjects of inquiry, it is quite certain that the heat which is generated in the combustion of the fuel exists under TWO perfectly distinct and very different forms. One part of it is COMBINED with the smoke, vapour, and heated air which rise from the burning fuel, and goes off with them into the upper regions of the atmosphere; while the other part, which appears to be UNCOMBINED, or, as some ingenious philosophers have supposed, combined only with light, is sent off from the fire in rays in all possible directions.
With respect to the second subject of inquiry; namely, how this heat, existing under these two different forms, is communicated to other bodies; it is highly probable that the combined heat can only be communicated to other bodies by ACTUAL CONTACT with the body with which it is combined; and with regard to the rays which are sent off by burning fuel, it is certain that THEY communicate or generate heat only WHEN and WHERE they are stopped or absorbed. In passing through air, which is transparent, they certainly do not communicate any heat to it; and it seems highly probable that they do not communicate heat to solid bodies by which they are reflected.
In these respects they seem to bear a great resemblance to the solar rays. But in order not to distract the attention of my reader, or carry him too far away from the subject more immediately under consideration, I must not enter too deeply into these inquiries respecting the nature and properties of what has been called RADIANT HEAT. It is certainly a most curious subject of philosophical investigation, but more time would be required to do it justice than we now have to spare. We must therefore content ourselves with such a partial examination of it as will be sufficient for our present purpose.
A question which naturally presents itself here is. What proportion does the radiant heat bear to the combined heat?--Though that point has not yet been determined with any considerable degree of precision, it is, however, quite certain, that the quantity of heat which goes off combined with the smoke, vapour, and heated air is much more considerable, perhaps three of four times greater at least, than that which is sent off from the fire in rays.--And yet, small as the quantity is of this radiant heat, it is the only part of the heat generated in the combustion of fuel burnt in an open Fire-place which is ever employed, or which can ever be employed, in heating a room.
The whole of the combined heat escapes by