1864.] Note on the Hailstorm of Thursday the 2ith March. 531 



perhaps one or two per square yard per second, and although they 

 increased in frequency and number during the fall, which lasted about half 

 an hour, they were at no time very thick, and were throughout accom- 

 panied by rain, which increased in proportion to the haiL As the 

 stones increased in frequency, so also they increased in size, and the 

 largest fell just before the end of the storm. 



The form and structure of the stones are noteworthy. They had all 

 of them a more or less oblate or discoid form, some being rudely 

 elliptical in section, while others, and especially the larger, were irre- 

 gular discs. The exterior was extremely irregular, resembling the 

 extremities of a mass of crystals, but I noticed no regular development 

 of crystalline faces. [It must, however, be remembered that the stones 

 were partially melted at the time of their touching the ground.] The 

 interior (nucleal portion) as seen in a fracture or a partially melted 

 stone, fig. 2a. PI. I. was formed by alternating opaque concentric bands 

 (of which in one case I distinguished 7) separated by rings of less 

 opacity, and the outer portion consisted of transparent ice containing 

 numerous air-bubbles.* The air bubble which escaped from the largest 

 of these when the stone was melted under water was as nearly as large 

 as a grain of mignonette seed. The arrangement of the air bubbles 

 was irregularly radiate. Many of the more discoid stones exhibited 

 deep depressions, almost amounting to holes, in their axis, as shown 

 in fig. 3. 



The largest of the stones which I noticed, are those represented in 

 figs. 1, 2. PL I. The dimensions of the latter of these, taken when first 

 picked up, were,— diameter 45 mm. thickness 27 mm. The stone, 

 fig. 4, is represented of its natural size, and its irregularity appears to 

 be due to the coalescence of two nuclei. It is the only one I noticed 

 exhibiting this phenomenon.! 



* Dr. Brandis lias since furnished me with the accompanying sketches of 

 sections of the stones made bj him during the fall. PI. IL He points out that 

 some had transparent, others opaque nuclei. I may also refer to these sketches 

 as independent evidence of the oblateness of form, which, as I have above 

 observed, characterized most of the stones. 



f This must have been due to an oversight on my part, and my having been 

 engaged in sketching the stones, &c. during the last 5 or 10 minutes of the fall. 

 Dr. Partridge who lives only at the distance of a furlong, and Dr. Anderson three 

 miles off, inform me that during the latter part of the fall, the majority of the 

 stones were agglomerated. Prom their description, these appear not to have 

 been larger than those simple concretions which I have figured. The weight of 

 the largest weighed by Dr. Anderson was 3 drachms. At the reading of fch© 



3 y 2 



