of the so-called Storm-glass. 



99- 



Nitrate of Potash in Crystals. 



32 drachms in 4 fluid-ounces of distilled water, 

 of room 49° F. 



Temperature 





Differ- 



Lower 





Upper 



Differ- 





Remarks. 



ence. 



thermo- 



Time. 



thermo- 



ence. 



Remarks. 



^» 





meter. 





meter. 









o 



6 



Boil- 228 

 ing 



h m 

 12 9 



Lamp 

 removed. 



Boil- 222 



ing 



O 







2 



210 



10 



208 











196 



12 



201 



5 





Ascending and de- 





184 



14 



190 



6 





scending currents 





170 



16 



179 



9 





very active. 





157 



19 



170 



13 









149 



21 



162 



13 









143 



23 



154 



11 





Crystals first no- 





140 



25 



146 



6 





ticed at the bot- 





140 



27 



143 



3 



Crystals forming on 



tom. 



2 



139 



29 



137 





surface and flakes 





1 



137 



30 



136 





falling from them. 





3 



136 



31 



133 









5 



137 



32 



132 





Fan-shaped masses 





6 



136 



33 



130 





of crystals pro- 





7 



134 



35 



127 





jecting from the 





8 



133 



36 



125 





surface down- 





9 



130 



38 



121 





wards. 





10 



130 



39 



120 





Fan-shaped crystals 





11 



128 



40 



117 





2^ inches long. 





11 



126 



42 



115 









10 



122 



44 



112 





Do. 3^ inches long 



Crystals increasing 



10 



120 



46 



110 





and 1 inch wide. 



from the bottom 



12 



118 



48 



106 







until the prisms 



12 



116 



50 



104 







rose to the height 



13 



113 



53 



100 







.of 3 inches and 



12 



111 



55 



99 







met those projec- 



11 



107 



59 



96 







ting from top. 



11 



105 



1 



94 







Lower thermometer 



18 



96 



10 



88 







buried in crystals. 



I 4 



74 



50 



70 







There are some points connected with the above experiment 

 which, taken in connexion with a similar experiment with sal-am- 

 moniac, seem worthy of attention. The difference between the boil- 

 ing points of water at the bottom and just below the surface was 

 noticed by Gay-Lussac*; but after the boiling has been stopped 



* Annates de Chimie, xlix. 394 (1832). " Suppose a volatile liquid of a 

 certain depth to be submitted to ebullition. Two thermometers plunged 

 into the liquid, one near the bottom, the other near its surface, will indi- 



H2 



