108 ON SNOW CRYSTALS. 



that a great range of temperature is not essential for the pro- 

 duction of this diversity. Among the configurations we ob- 

 served as identical with those of Scoresby, were two forms 

 (Jigs. 59 and 69) which had only once fallen under his ob- 

 servation. Dr. Nettis mentions that in one day and night 

 " he observed fifteen, twenty, or more particles of snow diffe- 

 rently formed ;" and by the observations of eight days, viz., 

 the 11th, 12th, 13th, 21st and 23rd of January, and the 6th, 

 23rd, and 24th of February, he was enabled to figure the 

 ninety-one crystals published in connection with his memoir. 

 The shower of crystals which we had the gratification of wit- 

 nessing, would seem in comparison to have been peculiarly 

 rich in diversity of figures. ■ 



The size of our crystals may next be noticed. Scoresby 



1 The following notice of their previous occurrence to me in England pre- 

 sents a remarkable difference in this respect : since it was published I have 

 not seen any record of these lamellar crystals having been observed in the 

 British Islands. " On the 22nd of March, 1833, when travelling outside a 

 stage coach from London to Shrewsbury, and near to Daventry, the day 

 being up to this time mild and calm, (the weather for some weeks previously 

 had been excessively cold, with prevalent easterly and north-easterly winds), 

 snow, of the loose fleecy kind common to the climate, began to fall, but 

 mingled with it there appeared beautifully delicate lamellar crystals, of 

 uniform transparency,having aspherical nucleus, from which sprang six and 

 twelve radii, most exquisitely formed, all the rays on each species being 

 equal, and not in a single instance deviating from the regularity of geome- 

 trical proportion, as has on some occasions been observed. By far the 

 greater number of these were of the former species, having six points radi- 

 ating from a centre." The figures 20 and 94 in the plates of snow crystals 

 in Scoresby 's 'Arctic Regions' represent both these crystals, the lines exhi- 

 bited as extending from the centre of the latter not having been however 

 visible to the naked eye." — Lond. & Ed. Phil. Mag. vol. v. p. 318. 



On this occasion two forms only of these crystals were observed, and it is 

 considered by Scoresby that Nos. 93 and 94, each having twelve spines, ap- 

 pear to be accidental varieties, and are produced probably by the correct 

 application of two similar crystals upon each other. If this opinion be cor- 

 rect, one normal kind only occurred, and merely the two forms having come 

 under notice may seem to favour this idea ; as may also the fact of the six 

 being much more numerous than the twelve pointed ones. Opposed to this 

 view however is the circumstance, that the twelve points on all I saw were 

 placed at equal distances, as they are figured by Scoresby, who does not 

 state that he ever observed any irregularity in them : but if formed by the 

 application of two six-sided crystals, why should not the points have occa- 

 sionally appeared at irregular as well as regular distances ? Of the two 

 forms seen in England, No. 20, or the six-sided, only appeared on this oc- 

 casion. Both days were alike calm ; the wind on the former was north, 

 with a point of east : on the latter south-east. 



Mr. Patterson was the first to observe the crystals at Belfast, and imme- 

 diately hastened to inform me of the circumstance, when I joined him, and 

 from our united observations the above article has been drawn up. — Wm. 

 Thompson. 



