134 PHILOSOPHICAL TRANSACTIONS. [aNNO J 737. 



second, except the small difference which must arise according to the given 

 distance, it will be a proof, that the refraction has been of no prejudice. 



The other considerable observations and experiments, to be made in the 

 journies undertaken for such inquiries, are, the observations of the magnetic 

 needle, both as to its dip and variation : but chiefly the observations of the 

 length of the simple pendulum, which at present is become requisite to be ob- 

 served with as much exactness, and in as many places, as is possible; but also 

 for which there are new methods invented, which probably surpass those hither- 

 to made use of; in as much as, since those methods have been found by the 

 the Royal Academy of Sciences of Paris, it was thought proper to notify them 

 to the astronomers sent to Peru, to put them in practice in their observations. 



The actual Mensuration of the Basis proposed in the preceding Article. By M. 



De Lisle. N° 445, p. 50. 



M. De Lisle undertook to measure the basis mentioned above, and had the 

 good fortune to measure it very exactly on the ice, by taking the precise distance 

 between the castle of Peterhoft', and the castle of Doubki, opposite to it, on 

 the coast of Finland. He found the distance between the opposite walls of 

 these castles to be 74,250 feet English. This basis, being much greater than 

 any of those employed hitherto for this purpose, gives room to expect great 

 exactness in the whole work, when it shall be carried on in the same manner. 

 It will at the same time serve to make a very exact map of the bottom of the 

 gulph of Finland. It is for the same design, and for better ordering the charts 

 of the coasts of the Baltic, that he intended (as soon as my project shall be ap- 

 proved here in its full extent) to begin to measure my triangles along the coasts 

 of Ingria and Livonia, to the islands of Dagho, Oesel, &c. And that the 

 charts of the places taken in by these triangles may be finished at the same time, 

 he designed to take with him all the charts of these parts, which could be had 

 to verify and correct them in his way. 



He likewise intended to publish, as soon as possible, all the operations and 

 observations made in the expedition; that thus early benefit may be reaped from 

 them, and that the public, at the same time the charts come out, may be ac- 

 quainted with the foundation on which they are constructed. 



Observations of two Parhelia, or Mock-Suns, seen Dec. 30, 1735; and of an 

 Aurora Borealis, Dec. 11, 1735. By the Rev. Timothy Neve. N''445, p. 52. 



On Tuesday, Dec. 30, J 735, between Cherry Orton and Alwalton, in the 



