10 



ASTRONOMICAL OBSERVATIONS 



EDINBURGH AND HUDSON. 

 MOON'S FIRST LIMB. 



Mean of 25 determinations from moon's first limb, 5A. 12m.52s.4. Mean difference, ±5s. 7. Probable error, ± Is. 0. 



MOON'S SECOND LIMB. 



| 1839, July 4,| 12wi. O.s.02 \5h.l2m. 3s.2 || 1839, Aug. 2,] 13m.18s.33 | 5A.13m. 5s.9 j 

 Mean of two determinations from moon's second limb, 5A.13m.4s.5. Mean difference, ± Is. 3. Probable error ±0.8. 

 Mean of twenty-seven determinations from both limbs, 5A. 12m. 56s. 4. 

 Longitude of Edinburgh, + 12m. 43s. 0. Longitude of Hudson, from Greenwich, 5h. 25m. 39s. 4. 



RESULTS. 



Longitude of Hudson, from 72 Greenwich observations, 5L25m.40s.6 

 " 33 Cambridge " 30 .2 



18 Oxford " 37 .8 



" 27 Edinburgh " 39 .4 



Mean of one hundred and fifty determinations, allowing double weight to the Green- 

 wich observations, bh. 25m. 39s.5. 



When all the European observations up to the present time have been published, we 

 may expect to obtain many new determinations of longitude. At present, I assume, for 

 the position of Hudson observatory, Northern Latitude, 41° 14' 42".6; Western Longi- 

 tude, from Greenwich, 5h. 25m. 39s.5. 



The transit instrument is 1399 feet north, and 919 feet cast of what is reported to be 

 the centre of Hudson township. We have, then, for the centre of the township, North 

 Latitude, 41° 14' 28".9; West Longitude, bh. 25m. 38s.7, a result of some importance to 

 geography, and differs sensibly from the position assigned on most maps. 



V. onSEHVATIONS OF COMETS. 

 1. Enckc's Cornel. 

 Encke's comet was observed in 1812, on the evenings of March 28, 30, 31 ; April 1, 4. 

 5, 7, 9, and 11. The mode of observation consisted in observing the times of ingress and 

 egress of the comet, and one or more stars of comparison. For this purpose, I employed 

 a positive eye-piece, with a magnifying power of fifty-eight, having five parallel and equi- 

 distant spider lines, crossed by as many others at right angles. The diameter of the 



