98 Mr. C. Tomlinson's Experimental Examination 



and extend it over the whole surface, and it would be found in 

 the morning dropping down the beautiful camphor feathers. A 

 journal of this bottle, kept during November and December last, 

 with the temperatures noted, satisfy me that heat is the efficient 

 agent concerned in the results. 



The effect of hermetically sealing the bottle seemed to be in 

 this case a diminution of the upper crust, which was thin and 

 scanty compared with what it was in another large bottle to 

 which the mixture was afterwards transferred, and where access 

 was had by a small opening to the external air. This is exactly 

 what would be expected ; for in the one case the space above 

 the liquid would always be saturated and prevent adhesion 

 between the surface and the air, while in the other case the 

 enclosed air would partake of the pressure and hygrometric 

 condition of the external air, and not only allow a crust to be 

 formed, but assist it in throwing off vapour of camphor, which 

 would condense on the coldest side of the glass above the mix- 

 ture, as already noticed. 



In order to ascertain the part that each ingredient plays in the 

 storm-glass mixture, it was examined separately under circum- 

 stances calculated to exaggerate the phenomena. A solution of 

 nitre, for example, was raised to the boiling-point in a long glass 

 similar to that of the storm-glass, and the phenomena which 

 accompanied its cooling, together with the temperatures at 

 the top and at the bottom, were noted. A similar experi- 

 ment was performed with sal-ammoniac, camphor-julep, spirits 

 of wine, and water. The vessel selected for the purpose was 

 a large test-tube of thin German glass, 8£ inches in length 

 and 1~ inch in diameter, suspended from the ring of a retort- 

 stand. Into this tube were poured 4 fluid-ounces of distilled 

 water, heat was applied, and 32 drachms of nitre were gra- 

 dually added, the last portions being suspended in a muslin 

 bag just below the surface. The solution was raised to the 

 boiling-point and left to cool in a room the temperature of which 

 was 49°. Two thermometers were kept in the solution, the bulb 

 of one penetrating to the bottom nearly in contact with the glass, 

 and the bulb of the other just below the surface of the solution. 

 Both the thermometers range well together, and their stems are 

 enclosed in tubes welded to the bulbs and sealed at the top. 

 The experiment was conducted about two feet from a window, 

 so that the effects could be watched by transmitted light. The 

 following Table gives the results of this experiment : — 



