148 



a shower which fell at Belfast on the 14th of January ; the 

 crystals appearing to constitute fully one-third of the snow- 

 that fell. Nineteen distinct forms were observed, and are 

 described in detail in the paper. Most of them are identical 

 with those delineated by Hooke, Nettis, and Scoresby ; there 

 are some, however, which do not appear to have been before 

 observed. They all belonged to the " lamellar," or first of 

 the genera into which they are divided by Scoresby. The 

 size of the crystals generally exceeded considerably that 

 of those observed by the above-mentioned authors ; their 

 average diameter being such that the naked eye could 

 readily discriminate the various figures, as they lay on a 

 dark ground. 



From the great variety of figures observed in the course 

 of a very limited time (a single hour) it is inferred by the 

 authors, in opposition to the opinion of Scoresby, that a 

 considerable range of temperature is not essential to the 

 production of very various forms. 



The weather for some days previous had been frosty, 

 and the barometer gradually falling from about noon on the 

 12th. On the morning succeeding the day in which the 

 observations were made, there was snow, succeeded by 

 showers of sleet ; and at noon a heavy rain set in, and con- 

 tinued without intermission the remainder of the day. 



The President, in presenting the copy of the Arenarius 

 of Archimedes, described in the donations of this evening, 

 stated that he had intended to offer some remarks on that 

 relic of mathematical antiquity ; but announced that he con- 

 sidered it unnecessary to do so, on finding that his remarks 

 had been, to a great extent, anticipated by Professor Rigaud 

 of Oxford. 



Professor Lloyd communicated the results of a paper 

 "on the Annual Decrease of the Dip in Dublin." 



It is well known that the dip has been diminishing in 



