VOL. L.] PHILOSOPHICAL TRANSACTIONS. 81 



which ihe sea perpetually covers, and have more than 30 feet water above them. 

 But these are sufficient to confirm the ancient tradition of these parts, that St. 

 Michael's mount, now half a mile inclosed with the sea, when the tide is in, 

 stood formerly in a wood. That the wood consisted of oak, very large, hazel 

 and willow trees, is beyond dispute. That theie has been a subsidence of the 

 sea-shores hereabouts, is hinted in a former letter; and the different levels and 

 tendencies, observed in the positions of the trees found, afibrd some material 

 inferences as to the degree and inequalities of such subsidences in general ; a« 

 the age in which this subsidence happened (near 1000 years since at least) may 

 convince us that when earthquakes happen, it is well for the country that they 

 are attended with subsidences; for then the ground settles, and the inflammable 

 matter, which occasioned the earthquake, has no longer room to spread, unite, 

 and recruit its forces, so as to create frequent and subsequent earthquakes; 

 whereas, where there are earthquakes without proportionable subsidences, there 

 the caverns and ducts under-ground remaining open and unchoaked, the sam6 

 cause, which occasioned the first, has room to revive and renew its struggles, 

 and to repeat its desolations or terrors, which is most probably the case of 

 Lisbon. 



X. Experiments on applying Dr. Hales s Method of Distilling Salt-water to the 

 Steam Engine. By Keane Fitzgerald, Esq. F. R. S. p. 53. 



On reading Dr. Hales's account of purifying salt water, by blowing showers 

 of air through, it occurred to Mr. F. that something of the kind might be ap- 

 plied with advantage to the steam or fire-engine, by increasing the quantity of 

 steam, and consequently diminishing the quantity of fuel otherwise necessary. 

 As the strength of steam raised from boiling water is always in a fluctuating state, 

 and has never been found above V^- stronger or weaker than air; he was in doubt 

 whether steam, produced by this method, would be sufficiently strong for the 

 purpose of the steam-engine. 



Mr. F. made an experiment first on a small boiler, about 12 inches diameter, 

 made in the shape of those commonly used in steam-engines, with a funnel at 

 the top, of about 1 inch diameter, for the steam to pass through, the aperture 

 of which was covered with a thin plate, fixed at one end with a hinge, and a 

 small leaden weight to slide on the other, in the nature of a steel-yard, to mark 

 the strength or quantity of the steam. A tin pipe made for this purpose, with 

 several small holes towards the end, passed from a small pair of bellows, through 

 the upper part of the boiler, to within about an inch of the bottom. The boiler 

 was half filled with water, which covered the holes in the pipe about 6 inches. 

 From the best observation he was capable of making with this machine, by 

 blowing air through the boiling water, it produced about \ more steam than was 



VOL. XI. M 



