Mechanical Science. 5 
bank of the river. Upon inquiry, I learned that this chimney 
belonged to a steam-engine, employed in a coal mine, and that 
it had been erected some years before, under the following cir- 
cumstances :— 
The engine had formerly been provided with a chimney of the 
ordinary kind, from which such volumes of black smoke were 
discharged, as to render it, when the wind blew in a particular 
direction, an intolerable nuisance to the town. 
When, therefore, the lease expired of the ground upon which 
the engine was erected, the Dean and Chapter (to whom the 
ground belonged,) refused to renew it except upon the condi- 
tion, that a chimney should be erected so high as to carry the 
smoke completely clear of the town. The condition was ac- 
ceded to; and a chimney was in consequence built, the summit 
of which was elevated upwards of one hundred feet above the 
fire-place. The experiment was completely successful, but not 
exactly in the manner which had been contemplated; for the 
town was relieved, not so much by the smoke being carried 
to a greater elevation than formerly, as by the change which was 
produced in the quantity and quality of that actually emitted. 
Nor had the proprietors any reason to regret the expense to 
which they had been put in erecting the new chimney; for the 
quantity of coal consumed by the engine was (as my informant 
stated) much less than formerly, and the consumption was so 
perfect, as to render all cleansing of the flue unnecessary. 
As the preceding account was received on the spot, and from 
a person employed in the works, it may, I believe, be considered 
as in general accurate; but as I cannot vouch for that accuracy 
from personal experience, I beg leave to suggest the propriety 
of inviting some inhabitant of Durham to corroborate or to cor- 
rect the statements it contains, M. 
The smoke-burning schemes have all ended in smoke, as we 
ventured to anticipate would be the ease in the article to which 
our correspondent M. alludes. There can be no doubt that no 
large engine in the metropolis, or near houses to which it can 
prove a nuisance, should be suffered to be erected without a 
chimney at least one hundred feet in height from the ground. 
9. Bridge of the SSa. Trinitd, over the Arno, at Florence.— 
A description of this celebrated bridge, erected in the middle 
of the 16th century by Bartolomeo Ammannatti Battiferri, illus- 
trated by plans, sections, elevations, and details of its various 
parts, has just been published by Mr. L. Vulliamy, who has 
lately returned to England from a very extensive professional 
tour through Italy, Sicily, Greece, and part of Asia Minor, in 
the course of which he has made many hundred drawings of 
