498 PHILOSOPHICAL TRANSACTIOX3. [aNNO 1779. 



through the smallest openings in the disc without any confusion. The time elapsed 

 between the first appearance of the sun's body through the aperture of the 

 moon's limb and the appearance of the sun's limb out of that of the moon will 

 serve to determine the depth of the said chink, aperture, or inequality, which 

 is equal to the height of the eminences which form it. The luminous point 

 was towards the north-west part of the moon's disc, a little more to the north 

 than the part of its limb through which that of the sun appeared at the 

 beginning of the emersion; and it is remarkable, that no other luminous speck 

 was perceived in the disc besides this. This aperture is therefore the only one in 

 thai }jart of the disc through which the emersion was to begin; whence we may 

 be certain, that throughout the 4th part of the moon's circumference, reachino- 

 from north to west, there is not any perceptible break in its limb besides that 

 which was then observed. There can be no doubt but that the luminous speck 

 which appeared through the aperture was part of the sun's body; this is demon- 

 strated by the red fiery colour (the same as that which is seen when this luminary 

 is looked at through a smoked glass) by its gradual increase in proportion as the 

 limb of the sun came near that of the moon, and in short by the colour, which at 

 its emerging was just the same as that which had been seen through the opening. 



It remains to be mentioned, that on the 24th of July, the day on which the 

 above observation on board the Espagne was made, the ship's latitude was 

 37° 14' north, measured the same day; that since noon it had sailed direct east; 

 that from the end of the eclipse to its being in the meridian of Cape St. Vincent it 

 had sailed 301 sea miles east, making 100 sea leagues, reckoning 20 leagues to 

 a degree; there remains to be known the difference of meridians of the said 

 Cape and the meridian of the different observatories of the capital cities of 

 Europe, in order to determine the part of the sea in which the observation was 

 made relatively to the observatories. 



The solar spots were seen very distinctly both before and after the eclipse; 

 there were 6 of them in all: 2 very near each other on the eastern part of the 

 disc; 2 towards the middle of the disc, also very near each other; and 2 

 towards the north, verging towards the north-west. The corrected altitude of 

 the sun's centre above the horizon, taken at the ihoment the eclipse ended, was 

 36° 31'. 



XII. On the Theory of Pile-Driving. Bij Tho. Bugge, Astronomer Royal, 

 and Professor of Astronomy and Mathematics in the Academy of Copen- 

 hagen. From the Latin, p. 120. 



Among the many conveniences afforded by mechanics to society, the art of 

 pile-driving is not the least. This art was not unknown to the ancients, as 

 appears by many passages in Vitruvius, though he does not particularly describe 

 the machine. P'or, without this art, it would be impossible to erect those 



