92 Transactions. — Miscellaneous. 



from maximum to minimum taking about three and a half days. The lapse 

 of a certain time alwaj^s occurring between the time of the lowest reading 

 of the barometer and the actual occasion of rain may be thus accounted for. 

 The desirabihty was also suggested of a simultaneous set of barometric 

 observations being made at the same place, but at different altitudes, in 

 order to determine the action of these vertical oscillations by direct experi- 

 ment. 



It is gratifying to learn that Professor Loomis has lately made valuable 

 experiments in this direction. He states, " that from observations on 

 Mount Washington, Pike's Peak, etc., both the maxima and minima of 

 atmospheric pressure generally occur later on as we rise above the surface, 

 the retardation amounting to one hour for an elevation of from 900 feet to 

 1,300 feet." Now, assuming that the retardation is uniform, then an oscil- 

 lation of three and a half days would correspond to an altitude of about 

 seventeen miles, and the great bulk of the earth's atmosphere is proved to 

 be below seventeen miles. 



Similar oscillations can be clearly traced on the diagrams of the Sydney 

 meteorological observations. 



Doubtless the original impulses, or first swings, were through the 

 agency of heat which caused the first uplifting of a portion of the atmo- 

 sphere far above the mean line of elevation. When the descending oscilla- 

 tion occurs it will not stop at a point corresponding to mean height and 

 pressure, but will by its momentum descend considerably below it, so that a 

 barometer at the earth's surface will stand at a pressure far above the mean. 

 The lower portions of the atmosphere are therefore compressed, and must 

 necessarily by their increased elasticity have stored up a force sufficient to 

 cause another ascending oscillation, which will again influence the barometer 

 and the weather. Generally after a few such oscillations they become lost 

 or masked by others. 



Their range is about one-thirtieth of the whole pressure of the terrestrial 

 atmosphere in medium latitudes, and they must I think, to a considerable 

 extent, lead to the formation of clouds in the upward oscillation, and to the 

 solution and disappearance of clouds in the downward one. These vertical 

 oscillations are, however, only local as far as our terrestrial atmosphere is 

 concerned ; at least it is not proved that general ones, embracing the whole 

 atmosphere, have been yet observed, though doubtless such have occurred 

 in earher times. 



We will now consider if similar movements, not only local but general, 

 cannot be traced in the sun's atmosphere and surroundings. 



Modern observations tend more and more to extend the height of the 

 solar atmosphere and surroundings ; some astronomers even approaching 



