182 



Corrections applied to the Great Meridional Arc, extending from Lati- 

 tude 8 9' 38"-39 to Latitude 18 3' 23"' 64, to reduce it to the 

 Parliamentary Standard. By Lieutenant Colonel W. Lambton, 

 F.R.S. and Corresponding Member of the Royal Academy of Sciences 

 at Paris. Read January 9, 1823. \Phil. Trans. 1823, p. 27.] 



It appears from the investigations detailed in this paper, that with 

 respect to a measurement on the meridian, the degree depending on 

 Colonel Lambton's brass scale must be multiplied by the fraction 

 000018, and the product subtracted from the measure given by the 

 scale to reduce it to the present parliamentary standard ; and that 

 the degree depending on Ramsden's bar must be multiplied by -00007, 

 and the product added to the measure given by the scale to reduce it 

 to the standard. 



On the Changes which have taken place in the Declination of some of 

 the principal fixed Stars. By John Pond, Esq. Astronomer Royal, 

 F.R.S. Read April 18, 1822. [Phil. Trans. 1823, p. 34.] 



The objects of this communication are chiefly two ; the first is to 

 restore a greater degree of confidence in the results of the late ob- 

 servations made with the mural circle at Greenwich, which now ap- 

 pear to have been subjected to a very small error only, arising from 

 some temporary causes now very eft 'ectually removed ; and the second 

 to point out a want of uniformity in the proper motions of almost all 

 the stars, which is of such a nature as to indicate a slow change of 

 place towards the south in almost every instance, with the exception 

 of y Ursse majoris, jS Ursse minoris, and j3 Cephei only. The greatest 

 deviation is found in three very bright stars, Capella, Procyon, and 

 Sinus. The proper motion of each of these is southward; hence 

 these proper motions are accelerated, while that of Arcturus, on the 

 contrary, may be considered as uniform. 



The author observes, that though the number of stars which have 

 proper motions northwards is nearly equal to those of which the pro- 

 per motion is southward, yet the joint magnitude of the motions 

 southward exceeds that of the motions directed northwards nearly in 

 the proportion of 4 to 1 . 



It was not till after February, 1821, that the mural circle became 

 completely out of repair ; its present perfection has been verified by 

 means of observations made with an artificial horizon of mercury 

 protected by wooden boxes, of different sizes and figures according 

 to the different altitudes of the stars : at the same time, Mr. Pond 

 observes, that for very delicate purposes it would be improper to 

 place implicit confidence in the observations of declination made in 

 the course of the year 1 820. 



