As to the quantity of fuel, that may be saved by this method, it is not easy to determine from any experiment on this engine, the boiler and fire-place of which is made very different from all others, and the quantity of fuel already thereby greatly lessened. The fire-place, which may be said to be within the boiler, and is but barely large enough to contain a quantity of the roundest and strongest burning coals sufficient to work the engine, cannot in this be made less; and consequently will not admit such a saving from this model, as from one properly constructed for the purpose: a proof of which I made, by trying some coals of a weaker kind, which were also cheaper; but on trial were not strong enough to work the engine, and had therefore been laid by. These coals answered extremely well; and, as it was a slower-burning coal, I found the consumption, whilst they lasted, was between two and three bushels less in every six hours, which is about the time the engine works each day: and I am satisfied, if the person, who attends the engine, would take the proper care, more coals could still be saved. For at several different times, when I had the coals exactly measured, and marked the time, I constantly found, that it required half a bushel in the hour less than he generally used, and the engine threw up as much water. As this method of blowing air thro’ boiling water, in order to increase the quantity of steam for a fire-engine, has, I believe, never before been attempted, and produces already a very good effect, I am in hopes it may be still further improved. XI. _Extract of a Letter of Mr._ Abraham Trembley, _F.R.S. to_ Tho. Birch, _D.D. Secret. R.S. Translated from the_ French. [Read Feb. 17, 1757.] Hague, 1 Feb. 1757. SIR, I Wrote to you on the 26th of November last, concerning the earthquake felt some time before between the Rhine and the Meuse. I have been since informed by Professor Donati of Turin, that a slight shock had been perceived there on the 13th of August 1756, at a quarter after nine in the morning. It was likewise felt in other parts of Piedmont. He has also communicated to me an extract of a letter of a professor of Genoa, one of his friends, of which the following is a translation. “On the 9th of November we felt here two shocks of an earthquake; one at 20¾ hours, according to the Italian way of reckoning; the other at about 4½ hours at night. I did not perceive the first, being then walking in the house; but I felt the second. I was then laid down, and going to sleep. The direction of the undulations was from north to south, as far as I could judge.”