286 PHILOSOPHICAL TRANSACTIONS. [aNNO 1772. 



above found, than might arise from the small errors of observation. Lastly, 

 from the several American observations collated together, are derived the follow- 

 ing values of p : viz. from the external contacts at Hudson's Bay and George 

 Island, p = 9.16 — 0.011?/ ; from the internal contacts at the same places p = 

 8.47 — 0.01 13/ ; from the internal contacts at Hudson's Bay and California p = 

 8.46 — 0.00963/; and lastly from the internal contacts at California and George 

 Island/) = 8.48 — 0.00123/. 



But now to find the true value of the correction y, for determining the abso- 

 lute value of the parallax p, it is observed that from tlie times of the internal 

 contacts it seems that this correction must be about 8", supposing the sun's semi- 

 diameter to be 946".38, which is a mean between the value of the semidiameter 

 assumed by M. Lalande, and that used by the English astronomers. Then this 

 value used for y, gives 8.'55 for the sun's parallax, and the semidiameter of 

 Venus 28".6, which must be within 2 or 3 tenth's of a second of the truth. But 

 if the correction of the latitude be a little less, and it is probably not below 5" by 

 the micrometer observations, this will not reduce the value of the parallax more 

 than the 50th part of a second. 



- Another calculation is made in two different ways, from the observations at 

 George Island; the one by combining the internal contact observed at the ingress 

 by Mr. Green, with the internal contact at the egress by Capt. Cook; and the 

 other, by a mutually change, by the observation of the former internal contact 

 of Capt. Cook combined with that of the latter by Mr. Green. The former 

 hypothesis gives the parallax p = 8.48 — O.OO8O3/, and the latter JS = 8.05 — 

 O.OOSOy, the mean between which, /> = 8.57 — O.OO83/, differs very little from 

 the former determination. 



X. On a New Chart of the Red Sea, with two Draughts of the Roads of Mocha 

 and Judda, and several Observations made during a Voyage on that Sea. By 

 I Capt. Charles Newland. p. 77- 



This chart oftheRedSea, was constructed from materials that Capt. N. became 

 possessed of, during his residence in the East Indies ; which chart, on his voyage 

 to Mocha and Judda, he experienced to be the best he ever saw. The only ma- 

 terial error he discovered in it, is, that the Abyssinian shore opposite Mocha is 

 placed too far to the westward by 25 or 30 miles, and that there are several 

 small islands on the same shore, not taken notice of in any chart. 

 Longitude of Judda by 12 distances of the ([ from ©. 



Worked by the British mariner's guide 39° 53' 45* 



And by the Ephemeris for 1 769 40 1 7 



Difference 7 22 



