[1] Eves and Sutton, bricklayers, Broad Sanctuary, Westminster, have alone altered above 90 Chimnies.--The experiment was first made in London at Lord Palmerston's house in Hanover-square;--then two Chimnies were altered in the house of Sir John Sinclair, Baronet, President of the Board of Agriculture; one in the room in which the Board meets, and the other in the Secretary's room; which last being much frequented by persons from all parts of Great Britain, it was hoped that circumstances would tend much to expedite the introduction of these improvements in various parts of the kingdom. Several Chimnies were altered in the house of Sir Joseph Banks, Baronet, K. B. President of the Royal Society. Afterwards a number were altered in Devonshire-house;--in the house of Earl Besborough, in Cavendish-square, and at his seat at Roehampton;--at Holywell-house, near St. Alban's, the seat of the Countess Dowager Spencer:--at Melbourne-house;--at Lady Templeton's in Portland-place; --at Mrs Montagu's in Portman-square;-- at Lord Sudley's, in Dover-street:--at the Marquis of Salisbury's seat at Hatfield, and at his house in town;--at Lord Palmerston's seat at Broadlands, near Southampton, and at several gentlemen's houses in that neighbourhood;--and a great many others; but it would be tiresome to enumerate them all; and even these are mentioned merely for the satisfaction of those who may wish to make inquiries respecting the success of the experiments. [2] Having been obliged to carry backward the Fire-place in the manner here described, in order to accommodate it to a Chimney whose walls in front were remarkably thin,--I was surprised to find upon lighting the fire that it appeared to give out more heat into the room than any Fire-place I had ever constructed.-- This effect was quite unexpected; but the cause of it was too obvious not to be immediately discovered.--The flame rising from the fire broke against the part of the back which sloped forward over the fire, and this part of the back being soon very much heated, and in consequence of its being very hot, (and when the fire burnt bright it was frequently quite red hot,) it threw off into the room a great deal of radiant heat.--It is not possible that this oblique surface (the slope of the back of the Fire-place) could have been heated red-hot MERELY by the radiant heat projected by the burning fuel, for other parts of the Fire-place nearer the fire, and better situated for receiving radiant heat, were never found to be so much heated;--and hence it appears that the combined heat in the current of smoke and hot vapour which rises from an open fire MAY BE, at least IN PART, stopped in its passage up the Chimney, changing into radiant heat, and afterwards thrown into the room.--This opens up a new and very interesting field for experiment, and bids fair to lead to important improvements in the construction of Fire-places.--I have of late been much engaged in these investigations, and am