3IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



fig. 43; the pressures and temperatures are given at the bottom. 

 These curves are curves of condition (Z Z) in the sense explained in 

 section (2) and are specially appropriate to set forth in clear light 

 the advantages of this method of representation. 



The curves t m of temperature and y m of average moisture directly 

 represent the results of observation. The values of /? m and y t are 

 then obtained by computation with the help of the temperatures 

 t m the first of them being computed step by step. 



To this latter circumstance is also to be attributed the fact that 

 irregularities in the course of the temperature curve must also pro- 

 duce others in the curves for /? OT and y m . 



The only results of computation exclusively are the barometer 

 readings] /? computed for various altitudes on the assumption of a 

 linear temperature gradient of i° per 100 meters. 



The values of /? a are added because it is not uninteresting to 

 present both numerically and graphically the law of diminution of 

 pressure for the impassable limiting case of the unstable equilib- 

 rium of dry air, and thus bring vividly to the eye the fact that 

 convective equilibrium establishes a limit not only for the rate of 

 diminution of temperature but also for that of pressure. 



Moreover, the dependence of the distribution of atmospheric 

 pressure on that of temperature finds a very instructive presenta- 

 tion by the comparison of the curves for /? OT and for /? a . 



Finally, in fig. 43, at the extreme right hand the adiabat for satu- 

 rated ascending air is added as a line of dashes and as it results accord- 

 ing to the tables constructed by Otto Neuhoff 9 and supplemented by 

 him for the highest altitudes, and assuming that the ascent began at 

 the ground at the temperature 18 C. 



At the first glance we see this curve has almost the same course as 

 that for the average temperatures and that by pushing it toward 

 the left it can be made to nearly cover that. It may, indeed, be 

 asked whether in this peculiarity there be not concealed a deeper 

 connection, at any rate the fact is so interesting that it should not 

 be passed by unnoticed. 



The value of the mode of presentation here used is especially evident 

 when we apply it not only to the general mean, but also to average 

 values for short intervals of time and when we set them beside 

 each other. 



• O. Neuhoff: Adiabatic changes of condition. for moist air and their deter- 

 mination numerically and graphically. Abhandlungen der Konigl. Preuss. 

 Met. Institute, Vol. I, No. 6. Berlin, 1900. (See No. XXI of this collection 

 of translations.) 



