VOL. LXXVII.] PHILOSOPHICAL TRANSACTIONS. 183 



X. Observations of the Tramit of Mercury at St. Petersburg. By M. Rumovski, 



Astronomer in the Imperial Academy. From the French, p. 48. 



The first internal contact 17^ 1"^ \Qt true time. 

 The last internal contact 22 26 55 very exact. 



During the passage, Mr. K. measured, with an objective micrometer, some 

 distances of the limbs, and the diameter of Mercury, which was sometimes T'.bQ, 

 and sometimes S".Qa, so that he takes the mean at 8''.2 or 8^4. Supposing the 

 sun's semidiameter 15' 52^', and his parallax 8'''.5, by 28 combinations he found the 



Time of the middle J 9^ 44"^ 37^ 



Time of the conjunction IQ 13 33. 



Geocentric longitude V 13° 50' V, 



Longitude of the node 1 15 53 56. 



Geocentric latitude O O 11 43. 



Least central distance 11 32. 



XI. On the Strata observed in Sinking for Water at Boston, Lincolnshire. By 



Mr. James Limbird, Surveyor to the Corporation, p. 50. 



May 7, 1783, George Naylor, of Louth, well-borer, began to bore at the 

 well in the Market-Place, Boston ; which had been sunk and bored to the depth 

 of 186 feet from the surface, in 1747, by Thomas Partridge. The well was made 

 about 6 feet in diameter at the top, 5 feet at the bottom, and 27 feet deep, and 

 the earth prevented from falling in by a circular frame of wood, which goes from 

 the surface of the earth to the depth of 2 1 feet 6 inches, and is there supported 

 by brick-work, laid on a bed of light-coloured blue clay, which continues to the 

 depth of 36 feet from the surface, where is a bed of sand and gravel about 1 8 

 inches thick, and under it the same sort of blue clay as before, which continues 

 to the depth of 48 feet from the surface. Below this is a bed of dark-coloured 

 stone, like rag stone, about 6 inches thick, from under which George Naylor 

 says, that a salt spring issues. Beneath this layer of stone, is a bed of dark-blue 

 clay, which continues to the depth of 75 feet from the surface, where is a bed of 

 stone, of a lightish colour, about 6 inches thick, and under it a bed of dark-blue 

 clay, which continues to the depth of 1 14 feet from the surface, where is a bed of 

 stone, of a brightish colour, about 8 inches thick, and under it a bed of gravel, 

 about 6 inches thick, where George Naylor says there is another salt spring. 

 Under the gravel is a bed of dark- coloured clay, resembling black-lead, which 

 continues to the depth of 1 74 feet from the surface, when it changes to a chalky 

 clay, intermixed with small pebbles and flints, which continues about 3 inches, 

 and then changes to the same kind of dark-coloured clay as before ; in which, 

 after boring to the depth of 186 feet from the surface, he came to the solid earth 



