TRANSACTIONS OF THE SECTIONS. 43 



Merebank, Maritz- 



near Durban, burg. 



1866 {continued). inches. inches. 



April 1-200 1-148 



»% 2-410 0-000 



June 0000 0-2o0 



July 1-210 0-410 



August 2-130 O'oOO 



September 3-980 TSoO 



October 4-370 1-100 



November 5-760 5-790 



December 3610 5-150 



48-540 30-266 



1867 



January 1-110 3-400 



February 5-410 5*660 



March 3-600 3-860 



April 6-890 3-140 



May 0-070 0-000 



June 1-260 0000 



July 0-160 0000 



August..' 0-430 0-370 



September 0-210 2040 



October 4-240 3-080 



November 5-490 6-690 



December 1-520 3-250 



33-080 31-490 



BemarJcs on Meteorolocikal Reductions, ivitli especial Reference to the Element 

 of Vapour. By Balfour Stewart, F.R.S. 



It -will be desirable to preface the method of reduction herein proposed by a few 

 remarks on the objects contemplated in such reductions. These objects are two- 

 fold. In the first place, meteorological reductions may be pursued -ndth the 

 immediate object ot acquiring information as to the climate of a place ; or 

 secondty, they may be pui-sued with the immediate object of extending cm" know- 

 ledge of meteorologj', regarded as a physical science. 



Ihus, for instance, a certain kind of reduction might be imagined to be of 

 immediate practical benefit in determining whether a certain place might suit a 

 certain class of persons or a certain class of plants, but yet it might not materially 

 advance our knowledge of meteorology, regarded as a physical science. But, on 

 the other hand, all observations tending to advance our knowledge of meteorology 

 are of undoubted practical benefit. The amount of vapour present in the air is 

 without doubt a very important element of climate, inasmuch as this aflects in a 

 marked manner the skin of the human body and the leaves of plants ; but I am 

 not aware that it has yet been determined bj^ the joint action of naturalists and 

 meteorologists what is the precise physical function which expresses proportionally 

 the effect of moisture upon animal and -vegetable life. Is it simply relative humi- 

 dity ? or does not a given relative humidity at a high temperature have a difierent 

 effect from that which it has when the temperature is lo-w ? 



There is, in fact, an absence of information as to the precise physical formula 

 which is wished by phj^siologists as expressing the effect of moisture upon organic 

 life. On the other hand, physicists may be presumed to confine themselves to 

 meteorology regarded as a physical science. It is in this latter aspect that I pro- 

 ceed to discuss the question. 



Regarding meteorology, therefore, as a physical science, it is one of our objects 

 to ascertain the distribution and laws of motion of the dry and wet components of 

 our atmosphere ; and it cannot be denied that we are at the present moment in 

 very great ignorance of these laws. 



