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 
