VOL. XX.] PHILOSOPHICAL TRANSACTIONS. 225 



best portable barometers. By the best of the two, I found the mercury de- 

 scended -rVof an inch at the height of 80 feet, and -^ at l6o feet. But since 

 that, finding my observations a little different from Mr. Halley's on Snowden- 

 Hill, I thought it necessary to renew my experiments more nicely ; and accord- 

 ingly last Nov. tried again with other portable barometers ; which erred into- 

 lerably. I therefore contrived to carry up the Torricellian experiment to the 

 top of the monument, thus: I provided a pretty large glass tube, well cleaned, 

 this I cased in wire, and filled with well strained mercury ; which being cleared 

 of air, I plunged the bottom of the tube into a broad cistern of mercury, and 

 then fixed both the tube and cistern together, in the wire case, or frame. 

 On the top I left an eye in the wire, to suspend the whole barometer on a 

 string, that it might hang pendulously, which is absolutely necessary ; be- 

 cause if the cistern be deeper on one side than another, or if the tube hang 

 more towards one side than the other, it will cause a great and erroneous 

 variation in the mercury above, according as the tube stands perpendicuiari) , 

 or not. 



My instrument being thus very nicely prepared, I marked exactly the height 

 of the quicksilver, on two narrow labels of paper, pasted on each side the tube, 

 both at the bottom, and in my ascent up the monument. The differences of 

 the mercury's height I measured with a decimal inch scale on thin brass ; and 

 the quantity of my ascent I measured with a Gunter's chain, because a string 

 would stretch. By the nicest observation I could make, I found that at the 



removed to the rectory of Upininster in Essex, where he continued till his death, which happened 

 in 1733, in the 78th year of his age. This situation, in the vicinity of London, gave him conve- 

 nient opportunities of conversing with learned men in the metropolis, and particularly with the 

 members of the Royal Society, to which he communicated a multitude of useful papers, sev..n' of 

 which were inserted in almost every volume of the Transactions, from the 20th, in 1698, to the 

 Syth vol. in 1735. Besides these, which exhibit strong indications of an active and philosophical 

 mind, he was autlior of several other ingenious works, as " Physico-Theology ; or A Demonstration 

 of the Being and Attributes of God ; from his Works of Creation;" being the substance of 16 

 sermons at Mr. Boyle's lecture, preached in 171I. And, in pursuance of the same design, in 1714-, 

 he published " Astro-Theology ; or, A Demonstration of the Being and Attributes of God, from a 

 Survey of the Heavens;" works which are still highly valued, and have passed through several 

 editions. The last thing he published of his own composition, was entitled, " Christo-Theology ; 

 or, A Demonstration of the Divine Authority of the Christian Religion." But besides his own, he 

 was useful also in perfecting or publishing some works of others. Thus, when Albin published 

 his natural history of birds and insects, it was accompanied with curious notes and observations by 

 our learned author. He also revised the Miscellanea Curiosa, published by Dr. Hallev, in 3 vols. 

 8vo. He published also some pieces of the celebrated Mr. Ray, revising and correcting that author's 

 manuscripts. To Dr. D. the world is likewise indebted for the publication of the Philosophical 

 Experiments of the ingenious Dr. Hook, and other learned men of his time. 

 VOL. IV. G G 



