552 PHILOSOPHICAL TRANSACTIONS. [aNNO I67I. 



Of the Stone Quarry near Maestricht. Communicated hy a Person 

 acquaiiited with that Country. N°6J, p. 2051. 



There is an excellent quarry, within cannon shot of Maestricht, on the very- 

 brink of the river Maese, lying in a hill, where there are about 25 fathoms of 

 rock and earth over head ; the length of the hill being of some miles, extend- 

 ing along the river towards Liege ; and near Maestricht having in breadth 

 some half or three quarters of a mile, but more farther off. This quarry has 

 one entry towards the river, where carts can pass with great ease, and unload 

 the stones on the brink of the river, the quarry within lying parallel to the 

 horizon or level, and elevated but very little above the river. 



This quarry, which has almost undermined the whole hill, affords one of the 

 most surprizing prospects, when lighted with many torches, that one can 

 imagine. For there are thousands of square pillars in large level walks, and 

 those almost every where above 20, and in some places many more feet high, 

 and all wrought with so much neatness and regularity, that one would think it 

 had been made rather with curious workmanship for an under-ground palace, 

 than that those pillars and galleries were made by quarriers, that did it only for 

 getting stone to build above ground. 



This quarry serves the people, that live thereabout, for a kind of impregna- 

 ble retreat, when armies march that way. For being acquainted with all the 

 ways in it, they carry into it whatsoever they would have safe, as well their 

 horses and cattle, as their moveable furniture, till the danger be over ; there 

 being so much room, that 40,000 people may shelter themselves in it. And 

 he that would attempt to seek them out in this vast wilderness of walks and 

 pillars, without an expert guide, would not only be in hazard of losing his 

 way, but of being knocked on the head at the corner of every pillar, where peo- 

 ple lurking in the dark with their carabines and fowling pieces, would have fair 

 opportunity to shoot them by the light of their own torches. 



An Account of some Books. N°67, p- 2052. 



I. Tracts written by the Honourable Robert Boyle, of a Discovery of the 

 admirable Rarefaction of the Air, even without Heat : New Observations 

 about the Duration of the Spring of the Air : New Experiments touching the 

 Condensation of the Air by mere Cold ; and its Compression without mechani- 

 cal Engines ; And the admirably differing Extension of the same Quantity of 

 Air rarefied and compressed. London, ] 670, in 4to. 



The main drift of these excellent tracts is, to invite the curious to observe 



