11 PHILOSOPHICAL TKANSACTI0N5, [aNNO 1776. 



minute after it reached the point of boiling water. On examining the instru- 

 ment, he found the bulb cracked, and the quicksilver fluid. 



Mr. H. imagines it is extremely difficult to ascertain the exact degree at which 

 quicksilver begins to freeze, because no particular alteration or circumstance 

 points out the moment of congelation, or even afterwards; for the quicksilver 

 in the tube still continues to i'all, and has the same appearance as before, con- 

 trary to what we observe in water. He thinks therefore it can only be deter- 

 mined by breaking the glasses at different altitudes; but this would be both tedi- 

 ous and expensive. However, were spare tubes filled by the maker, and gra- 

 duated by the operator, to be made use of, the ex|)ence would be less; hut then, 

 if those tubes will not admit of being graduated, to a considerable distance, sup- 

 pose lOOO", below O, the operator is obliged to put a thermometer, with a scale 

 graduated by the instrument-maker, together with the other tube, into the mix- 

 ture, to learn the degree of cold after the quicksilver in the spare tube, desio-ned 

 chiefly for the experiment, has subsided into the bulb. Professor Braum made 

 t subside even to 1500", which shows the fineness of the tubes he made use of. 



By a great number of observations on the dipping needle, at Albany-Fort, 

 longitude 83° 30' west, latitude 52° 24' north, Februarys, 1775, the mean of 

 all was 79° 17i'- When the observations were finished, he turned the index 

 south, when the needle pointed at 89° 56', or very nearly perpendicular. He 

 cannot account for the differences, more especially as he took so nmch pains to 

 render these observations correct. 



Similar observations on March 13, 1775, gave for the mean 79° 25i'. 



And like observations on May 6, 1775, give a medium of 79° 28f'. 



XI. Astronomical Observations made in the Austrian Netherlands in 17 72 and 

 1773. By Nathaniel Pigolt, Esq., F. R. S. p. 182. 



At Namur, 1772, by a mean of 8 meridian altitudes of the fixed stars taken 

 in September, Mr. P. determined the latitude of his observatory, in the Rue St, 

 Nicholas, near the RecoUets Church, 50° 28' 32" north. And by an observa- 

 tion of the first satellite of Jupiter, compared with one at Paris, he determined 

 the longitude of Namur, 9"" 39% or 2° 24' 45", east of Paris observatory. 



In like manner, for Luxembourg, he determined the latitude to be 49° 37' 6" 

 and the longitude 15"^ 27^ of time, east of Paris observatory, by a mean from a 

 lunar eclipse and many eclipses of Jupiter's first satellite. 



At Luxembourg, 1772, Oct. 22, at 3 hours, p. m. a magnetic needle of 4 

 inches, made by Dollond, gave the declination west 18° 42-i-'. And Oct. 23, at 

 10 hours, a.m. the declination was 18° 50'. 



