MH. \V. N. SHAW OX HYOKo.M KTKK ' MKTIIODS. 





in the case of a thermometer which has its bulb covered with a thin layer of any 

 material. From this he is led to test the effect of ventilation upon the psychrometer, 

 and the observations given show a considerable depression of the temperature of the 

 wet bulb in consequence of the current of air produced by the double-fan arrangement 

 by the Tecnomasio of Milan. BELLI originally suggested the reading of wet-bulb 

 thermometers contained in a metal tube through which air was driven, and the 

 suggestion was practically carried out in an instrument designed by BUZZETTI, but 

 the new arrangement of the Tecnomasio gave a much stronger current than the 

 original apparatus of BUZZETTI, and from CANTONI'S observations it would appear that 

 the temperature of the wet bulb might be depressed often more than a whole degree 

 by the stronger current of air. 



A further contribution to the discussion of psychrometric observations lias been 

 made by ANGOT,* whose report is printed in full in the ' Annales du Bureau Central 

 Me'te'orologique,' 1880. Starting from REGNAULT'S general form 



and writing it 



x=f A.(t t')h, 



A- 

 - 



he determines the value A for each of 3670 comparisons between psychrometer 

 and dew-point observations made at Paris (height 40 metres), at the observatory of 

 the Puy de D6me (height 390 metres), or at the station on the summit of the Puy de 

 D6me (height 1470 metres). Of these, 282 observations gave the temperature of the 

 wet bulb below C. The range of the wet bulb temperatures was from 20'5 to 

 + 23'6 C., and the difference of the wet and dry bulb readings reached 16 C. The 

 dew-point instrument was ALLUARD'S modification of REGNAULT'S arrangement. t 



Having thus obtained a series of values for A, ANGOT found the mean of the values 

 for temperatures of the wet bulb lying between C. and 1 C., between 1 C. and 

 2 C., and so on for each station. 



The means in every case showed that the value of A depended on the value of 

 / t'. The following is cited an an example : 



'Journal de Physique,' vol. 1, 1882, p. 119. 

 t See below, p. 141. 



