In 1801 Messrs. Roberton, of Glasgow, patented some improvements upon Mr. Watt's plans, which rendered the apparatus more complete and convenient. To these gentlemen, indeed, is usually attributed the first successful application of the principle patented by Watt, of burning the smoke owing, we are inclined to believe, to the indifference of the public in the early part of Mr. Watt's career to the nuisance of dense smoke; as, from the comparatively small number of engines at that time, the adoption of means to burn the smoke was not so much sought after. Joined to this circumstance may be reckoned the unskilful manner in which bricklayers, pretending to an adequate knowledge of the subject, executed the work; which caused the principle to get into disrepute, rather than the bungling attempts to carry it into effect. It was, in consequence, given in evidence, by numerous witnesses before a committee of the House of Commons, that more coals were consumed by burning the smoke than allowing it to pass off unconsumed! in other words, that inflamed gas afforded less heat than cold smoke.

The probability is, that more air was admitted than was requisite to supply the necessary quantity of oxygen to the carbonaceous matter, and that in consequence of such management, the temperature of the furnace or of the boiler was reduced, requiring an additional quantity of fuel to get up the requisite heat.