VOL. LXIII.] PHILOSOPHICAL TRANSACTIONS. 371 



house of Mr. Joseph Moulde, in Lombard-street, which was provided with a 

 round iron conductor, half an inch thick, its several lengths screwed together, 

 so as to make very good joints, and the lower end 5 or 6 feet under ground ; 

 the lightning leaving every thing else, pursued its way through that, melted off 

 6 inches and a half of the slenderest part of a brass wire fixed on the top, and did 

 no further damage within doors, or without. 



VII. Of an Experiment made with a Thermometer, whose Bulb was painted 

 Black, and exposed to the Direct Rays of the Sun. By Richard JVatson,* 

 D. D., F. R. S. p. 40. 



During the hot weather, in the latter end of June and the beginning of July 

 last (1772), Dr. W. made the following experiments at Cambridge. He exposed 

 the bulb of an excellent thermometer to the direct rays of the sun, when the 

 sky was perfectly free from clouds: the mercury rose to 108° of Fahrenheit's 

 scale, and continued stationary. A fancy struck him, to give the bulb a black 

 covering; this was easily effected by a camel's hair pencil and Indian ink; the 

 mercury sunk a few degrees during the application of the coating, and the eva- 

 poration of the water; but presently after rose to 118°, or 10° in consequence of 

 the black coat with which he had covered that part of the bulb which was ex- 

 posed to the sun. If the bulbs of several corresponding thermometers were 

 painted of different colours, and exposed at the same time to the sun, for a given 

 period, some conjectures, respecting the disposition of the several primary co- 

 lours for receiving and retaining heat, might be formed, which could not fail of 

 being in some degree interesting. 



VIII. A Report of the Committee appointed by the R. S., to Consider of a 



Method for Securing the Poivder Magazines at Pur/leet, p. 42. Dated 



Aug. 21, 1772. 



The society being consulted by the Board of Ordnance, on the propriety of 

 fixing conductors for securing the powder magazines at Purfleet rom lightning, 

 and having done us the honour of appointing us a committee, to consider the 

 same, and report our opinion; we have accordingly visited those buildings, and 

 examined, with care and attention, their situation, construction, and circum- 

 stances, which we find as follows : 



They are 5 in number, each about I-60 feet long, and aooui 52 feet wide, 

 built of brick, arched under the roof, which in one of tnem s slated, with a 

 coping of lead 22 inches wide on the ridge from end to end ; and the others, as 

 we were informed, are soon to be covered in the same manner. They stand 

 parallel to each other at about 57 feet distance, and are founded on a chalk rock^ 



♦ The present Bishop of LlandafF. 

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