5S^. PHILOSOPHICAL TRANSACTIONS. [aNNO 1774. 



the two stations, from 40°, so is the height of the upper station found nearly, 

 to the correction of the same: which added or subtracted, according as the mean 

 altitude of Fahrenheit's thermometer was higher or lower than 40°, will give the 

 true height of the upper station above the lower, in English fathoms; and mul- 

 tiplied by 6, will give it in English feet. 



The same rule, adapted to the thermometers of particular scales, is this : 

 take the difference of the tabular logarithms of the observed heights of the ba- 

 rometer, at the two stations, considering the first 4 figures, exclusive of the 

 index, as whole numbers, and the 3 remaining figures to the right as decimals; 

 and subtract or add the difference of the thermometer, of a particular scale, at- 

 tached to the barometer, at the two stations, according as it was highest at the 

 lower or upper station, and you will have the height of the upper station above 

 the lower one, in English fathoms, nearly; to be corrected as follows: make 

 this proportion; as 1000 is to the sum of the altitudes of the thermometer of a 

 particular scale, exposed to the air at both stations, so is the height of the upper 

 Station above the lower, found nearly, to, the correction of the same; which 

 added or subtracted, according as the sum of the altitudes of the thermometers, 

 exposed to the air, is positive or negative, will give the true height of the upper 

 station above the lower in English fathoms ; and multiplied by 6, will give it in 

 English feet. 



XXI. Eclipses of Jupiter s Satellites, observed near Quebec. By Sam. Holland, 

 Esq., Surveyor General of Lands for the Northern District of Americh. p. 171. 

 These eclipses of Jupiter's satellites were observed at a house, bearing south 

 36° west from Quebec, distant from the castle of St. Lewis 24- miles, with Dol- 

 lond's long reflecting telescope. 



r 



satellite. 



1770. Mean time. 



April ly. . . . 14" ^^ 21' immersion of the 2d "] 



M^y 1 12 42 32 1st 



' 14. ...12 5 30 2d I 



; 0:, not exact to 4" through the tliickness of the atmosphere 



21 13 41 30 2d 



2+ 12 52 20 1st J 



XXII. Observations of the Immersions and Emersions of the Satellites of Jupiter, 

 taken in 1768, by Ensign George Sproule, of U. M. 5Qth Reg., on the South 

 Point of the Entrance of Gaspee Basin, ivhich bears from Cape Ferrilong, or 

 the Cape forming the Bay to the Northward, N. 68}- ff''. by the true Meri- 

 dian, distant 12^ Marine Miles. Communicated by the j^stron. Royal, p. 177- 



The latitude of the place of obser\'ation, at Gaspee, accurately determined, 

 was 48° 47' 31". The variation of the needle, by repeated trials different ways, 

 was 16° 30' w. 



