594 KEPOBT— 1887. 



In the compilation of this index OA'er three hundred authors, weather bureaux, 

 and libraries have most heartily contributed ; nearly everj' nation in the world has 

 cheerfully responded to the call for information. The bibhographer, Mr. 0. J. Sawyer, 

 and his clerks have been employed continuously for three years, and in a few months 

 the question will be submitted to the national government whether such an 

 index is not worth publishing in full for the benefit of the whole world. It has 

 become, in fact, an international work, and its publication is the only means by 

 which a fair return can be made to co-operating scientists, and by which it can be 

 assured against destruction by fire or accident. 



At present a small case of drawers contains these fifty thousand cards. Who- 

 ever wishes to know what has been written on a given subject has but to consult 

 the proper drawer and section, and the response comes quicldy and fully. The in- 

 formation is as often desired by practical men as it is by the students and 

 the professors ; to them all it is, like the index rerum, an indispensable working tool. 

 It does not seem likely that any publisher wiU be able to print such a bibliography 

 at a price that will bring it within the reach of the students who need it the most. 

 Every similar work that has been successful has been compiled, and, at least in part, 

 published with Government aid, and we hope that the Congress of the United 

 States will make this important international work of the Signal Oftice as freely 

 available as are its daih' weather predictions, its monthly weather reviews, its 

 iuternational maps, and other publications. 



4. Fourth Report of the Committee appointed to co-operate with Mr. E. J. 



Lowe in his project of establishing on a permanent and scientific basis a 

 Meteorological Observatorij near Chepstow. — See Reports, p. 39. 



5. Second Beport of the Committee appointed to co-operate with the Scottish 



Meteorological Society in making Meteorological Observations o» Ben 

 Nevis. — See Reports, p. 34. 



6. On the Hygrometry of Ben Nevis. By H. N. Dickson, 



This paper gives an account of observations which were undertaken for the pur- 

 pose of testing the applicability at high-level stations, such as Ben Nevis Observa- 

 tory, of existing tables and formula for calculating the dew-point and humidity 

 from the readings of wet and dry balb thermometers. The construction of the 

 direct hygrometer used, that of Professor Chrystal, is described, and the action of 

 the wet and dry bulbs under different meteorological conditions is examined in 

 considerable detail ; the results showing that for investigations of this kind a great 

 range of humidity is necessary, the indications of the wet and dry bulbs being very 

 uncertain when the difference between them is small. 



The reduction of the observations is performed in the first place by a graphic 

 method, from which the following expression is deduced : — 



f-f'={t-t')!c, 



f being the vapour pressure at tne temperature t' of the wet bulb,/" that at tha 

 temperature of the dew-point, and t the air temperature. 



The truth of the above equation being assumed, the values of the quantity k 

 are next found by direct calculation from the observations. The available obser- 

 vations — numbering in all about 300 — make it possible to give fairly approximate 

 values for each degree of temperature of the wet bulb from 13° to 45° F. A 

 sudden large change takes place at the freezing-point and a similar, though much 

 smaller, discontinuity is shown to occur when the wet bulb stands between 39" 

 and 40° F. Below 32° F. the quantity \\h appears steadily to increase from 26 to 

 61, while between 32° and 39° F. and from 40° F. upwards its values remain 

 nearly constant at about 96 and 111 respectively. 



