242 TENTH ANNUAL REPORT OF 



witli some degree of precision, it will he expressed by adding to the 

 letter wliicli designates the direction, the figure indicating its force : 

 e. g., N, without a figure, signifies a slight air, hardly perceptible, 

 coming from the north ; Nj, a slight breeze ; N3, a strong wind, &c. 

 The other two columns will have only letters^ or a dash ( — ) if the 

 observation has not been possible. 



The quantity of clouds, or the cloudiness estimated from zero, or a 

 perfectly clear sky, to 10, sky entirely overcast, has a separate column. 



It is the same with 7^ain and melted snotv, which will be separately 

 entered. A third column is reserved for the total quantity of both. 

 The thickness of the layer of fallen snow may be indicated in inches 

 and tenths. 



As to the broad column reserved for the asjject of the shj, and^ re- 

 marhs, although it is desirable, considering the small space the form 

 of the table allows, to employ abbreviations to express the state of the 

 sky and the different meteorological phenomena ; nevertheless, we 

 must limit ourselves to a small number, chosen from am^ong the ex- 

 pressions which most frequently occur, such as those found at the 

 bottom of the blank forms. If abbreviations are too much multiplied, 

 we lose in clearness and certainty what we gain in conciseness. A 

 meteorological journal should not resemble a page of algebra, where 

 a badly formed letter or a misplaced sign renders the expression unin- 

 telligible. 



For the additional observations the same rule should be followed. 



In the space reserved for ^periodical and extraordinarij pJienomena, 

 the phenomena will be inscribed with their dates and the hour of their 

 appearance. 



Every change of position, or in the condition of the instruments, 

 should be carefully entered under the head of Condition of the instru- 

 ments^ with the precise date at which it took place. If there has been 

 none, instrumeids all in order will be entered . By the side of the indication 

 of the correction of the instruments will be placed, correction applied 

 or correction not applied, according as the observations contained in the 

 sheet shall have been corrected or not. The finished sheet will be 

 signed by the observer. 



The reductions, the corrections, and the calculations of means, must 

 be made day by day and at the end of each month with the greatest 

 imnctuality. The necessary tables will be placed at hand by the side 

 of the journal, and each observation reduced, and the correction, if 

 any, applied immediately. 



This is not only the least troublesome method, but the only one 

 which permits the observer to control the observations and the reduc- 

 tions, and to discover the accidental errors of the pen and of the read- 

 ing in the record. 



The observer cannot be too thoroughly convinced that a meteor- 

 ological journal which contains only rough observations, is only half 

 made; in this condition it is wholly unfit to serve any scientific pur- 

 pose. The observations cannot be compared rigorously with each 

 other, nor with those of other stations. The only means for the ob- 

 server to give its true value to his labor, is to make the corrections, 

 the reductions, and the calculations of the means himself. It is for 



