8 MR. A. W. WATERS ON CERTAIN LINES 



the straight-sided hexagon ; this then melted further, 

 leaving a crystal with the shape of the next interior lines. 

 When we see it taken to pieces we may judge that it 

 was built up in somewhat the same manner — that is 

 to say, by a growth from one form to another ; so that, 

 on the simple tabular hexagon, growth takes place 

 along the six sides, or from the corners arms may be 

 thrown out ; and such changes may, as my figures show, be 

 repeated several times. But, to explain the curved line 

 found in the interior, we must examine a little further. 

 When a crystal begins to melt, it loses the angular corners 

 and gradually melts down, so that we can suppose a crystal 

 G, thawing down, to take the shape of the meander line. 

 This brings us to the explanation of these curved lines, 

 which indicate, in the first place, a thawing; but as the arms 

 extend beyond these lines, it is clear that after this partial 

 thawing, freezing has begun again. 



The production of these lines thus shows that the crys- 

 tals, after having been formed in a cold atmosphere, have 

 passed into a warmer one, where part of the crystal has 

 been removed by thawing ; after this it has again passed 

 into colder air, and has formed anew upon the partially 

 melted crystal. 



It seems to me that these crystals bring down with them 

 registers of the comparative temperature of regions inac- 

 cessible to the meteorologist, and that a systematic exami- 

 nation in favourable localities would add much to the 

 knowledge of this science, as we may thus learn where 

 countercurrents exist. To take the crystal Gr, which fell 

 on the 22nd of December 1870, the meteorological obser- 

 vations for Switzerland show that the prevailing wind east 

 of Davos was north or north-east, with thermometer falling, 

 while to the west the wind was south and west. The con- 

 clusion which I have arrived at from the lines under con- 



