1876.] H. F. Blanford — Experiments with the Psychromeier. 61 



Assuming the direct dew-point determinations to be correct, the fol- 

 lowing are the errors shewn by the several computations. 



Table II. — Errors of Dew-points computed from Psychrometer hy 

 different methods. 







1 





Errors. 









Series 



D. P. 



below 











Place. 









Conditions. 







air. 



Aug. 



Apj. 



Glaish. 





Secunderabad, . . 



1 



44-7 



+ 2-5 



+ 6-1 



+ 5-4 



\ 



Do. 

 Do. 



2 

 3 



41-0 

 44-0 



+ 3-3 



+ 4-9 



+ 5-9 

 + 8-0 



+ 3-4 

 + 5-6 



> In thermometer-sued. 



Do. 



4 



41-9 



+ 3-9 



+ 7-0 



+ 4-6 



) 



Bellary, 



5 



40-7 



— 0-4 



+ 2-8 



+ 0-9 



\ 



Do. 



6 



P37-0 



?— 7-0 



?— 3-3 



?— 4-7 



[ Do. 



Do. 



7 



43-7 



— 2-0 



+ 1-9 



+ 0-9 



Do. 



8 



48-3 



— 4-6 



+ 0-6 



+ 1-6 



) 



Combatoor, 



9 



48-1 



+ 0-5 



+ 4-6 



+ 3-8 



) 



Do. 



10 



49-6 



+ 1-9 



+ 6-1 



+ 5-5 



) Do. 



Do. 



11 



42-9 



+ 0-3 



+ 3-8 



+ 1-9 



J 



Trichinopoly, 



12 



18-5 



+ 0-7 



+ 1-7 



— 1-6 



In verandah. Sling- 

 thermometers. 



Madras, 



13 



31-1 



— 0-3 



+ 2-3 



— 0-5 



Do. Do. 



Calcutta, 

 Do. 



14 

 15 



13-0 

 6-3 



— 0-4 

 + 0-5 



— 0-1 

 + 0-8 



— 1-6 



— 0-5 



| In sitting room. Do. 



Allahabad, 

 Do. 



16 

 17 



29-3 

 41-4 



+ 0-2 

 + 1-8 



+ 3-0 

 + 5-4 



+ 2-9 

 + 5-4 



| In verandah. 



Agra, 



18 



45-1 



— 6-1 



— 0-2 



+ 37 



Do. 



Lahore, . , 



19 



42-9 



+ 4-6 



+ 8-2 



+ 87 



Do. 



Do. 

 Do. 



20 

 21 



354 

 37-6 



— 2-9 

 + 0-8 



■H 1-4 

 + 4-6 



+ 3-2 



+ 6-7 



1 In thermometer-shed. 



Mean,* 



•• 



•• 



+ 0-46 



+ 3-70 



+ 3-00 





In most of the above series the computed is higher than the observed 

 dew-point, especially when the computation is made by Apjohn's formula. 

 The exceptions are series 6 at Bellary (in which, however, I think the 

 dew-point observation is open to considerable doubtf) and series 14 at 

 Calcutta and 18 at Agra, in which the computed values are too low. 



The following table exhibits the mean results of the table of errors, viz., 

 the numbers of sets of observations which give excessive or deficient dew- 

 point temperatures, the mean error, the extreme errors and the sums of the 

 squares of the errors, positive and negative, by each method of reduction. 



* Omitting series 6. 



f It is not unlikely that there has been some error in the determination of the 

 dew-point by the direct method, which, it may be observed, is derived from 2 observa- 

 tions only (one of deposition and one of disappearance). These observations wore taken 

 in among the 7 of the preceding series, and I have separated them on account of their 

 discrepancy. I have not, however, felt justified in rejecting them, since I have no 

 knowledge of any cause of error affecting them which might not have affected others, 

 9 



