VOL. LVIIl."] PHILOSOPHICAL TRANSACTION'S. 5/^ 



N. B. The clock was firmly screwed to a piece of timber, 22 inches in breadth 

 and 5-J- inches thick; the piece of timber was let 4 feet into the ground, which 

 was composed of a very firm, dry, hard clay. The ckx^k was placed in a tent, 

 with Fahrenheit's thermometer hung to its side ; and a blanket was wrapped round 

 the clock and thermometer, to secure it from any wind that might enter the 

 tent. The pendulum was adjusted to the upper scratch, with N° 3 at the index, 

 as directed by the Rev. Mr. Maskelyne, Astronomer Royal : but the spring at 

 the suspension of the pendulum having been broken (when the ship, in which it 

 was sent, was wrecked on the Jersey coast) we cannot be certain that the pendu- 

 lum is now of the same length as it was when sent from London. 



A journal is then given of the height of the thermometer observed 2 times a 

 day; also of the extent of the arch vibrated by the pendulum, which was com- 

 monly from 1° 35' to 1° 40' on each side of the perpendicular. But no inference 

 is drawn touching the difference of gravitation ; probably owing to the uncer- 

 tainty of the length of the pendulum by being broken. 



XLIV. On the Extraordinary Heats observed at Rome this last Summer. By 

 Mr. James Byres. Dated Rome, jiug. 27 , 1768. p. 336. 



The excessive heat of this summer is much greater than has been known in 

 Rome for many years. Friday, the 19th instant, the mercury in a well-regu- 

 lated thermometer according to Fahrenheit's scale, exposed at a north window, 

 where there was no sun and very little reflection, stood from 10 o'clock in the 

 morning until about 5 in the evening at 99. About half an hour after sunset it 

 fell to 90, and at midnight was fallen to 85, where it remained all night. This 

 is the hottest day we have had ; but for these 3 weeks past at mid-day the mer- 

 curj' has been always above 94, and at midnight seldom under 83; which is the 

 more extraordinary as he did not remember to have observed any other summer 

 above 89 at mid-day, nor above 75 at midnight. Notwithstanding this great 

 heat, there was never a more healthy summer at Rome; all the hospitals are al- 

 most empty. 



XLV. y/ra Easy Method of Making a Phosphorus, that will Imbibe and Emit 

 Light, like the Bolognian Stone; with Experiments and Observations. By 

 John Canton, M.J., F.R.S. p. 337. 



To make the Phosphorus. — Calcine some common oyster shells, by keeping 

 them in a good coal fire for 4- an hour ; let the purest part of the calx be pul- 

 verized and sifted; mix with 3 parts of this powder one part of the flowers of 

 sulphur; let this mixture be rammed into a crucible of about l-i- inch in depth, 

 till it be almost full ; and let it be placed in the middle of the fire, where it must 

 be kept red hot for one hour at least, and then set by to cool: when cold turn it 

 out of the crucible, and cutting or breaking it to pieces, scrape off", on trial, the 



4 £ 2 



