42 INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 



tions at a station, the graph (Form No. 1115-Aer.) of the first form 

 used and on the reverse side of which the data are entered for ascen- 

 sion No. 1 will be left blank. The graph for ascension No. 1 will 

 then be drawn on the second form, on the reverse side of which the 

 data for ascension No. 2 are to be entered. For the last observation 

 on December 31 of each year the Form No. lllOA-Aer., on the re- 

 verse side of which the graph for the last observation is drawn, should 

 be left blank and a new form used for the first observation on January 

 1 of the next year. Only the data on Form No. lllOA-Aer. are to 

 be entered on this first form of the year, the reverse side (Form No. 

 1115-Aer.) being left blank. Carbon copies on plain paper are to 

 be made of all original entries on Form lllOA-Aer., and these copies 

 are to be retained as a permanent station file. When time does not 

 permit the construction of the graph, immediately after completing 

 Form No. lllOA-Aer., data for current use and teletype or telegraph 

 reports may be taken directly from the latter form by interpolation. 

 A quick and convenient mental conversion of meters per second into 

 miles per hour may be made as follows: Double the m, p. s., take 

 the tens of the result (disregarding decimals), plus 1, and add to the 

 figure obtained from doubling the m. p. s. The result is miles per 

 hour. To convert 17.4 m. p. s. to m. p. h., for example: Multiply 

 17.4 by 2 and we have 34.8 (i. e., 3 tens); adding one to the 3 tens 

 makes 4, and adding 4 to 34.8 gives a total of 38.8 m. p. h. (reported 

 as 39). 



131. Form No. 1115-Aer. (combined with Form No. lllOA-Aer.) 

 figure 14, is a graphical representation of the data obtained from the 

 ascension. The construction of the graphs has already been explain- 

 ed in section IV. The heading on this form should agree in all details 

 with that of the corresponding Form No. lllOA-Aer. Form No. 

 1115-Aer. will be rendered only whf>n an ascension is made. WTien 

 an observation results in no ascension (i. e., the balloon is lost before 

 reaching an altitude of 1,000 feet above the surface) the reason for 

 same will be entered in the upper right-hand corner of the succeeding 

 form under the heading printed thereon for that purpose, as follows: 



Cause 

 Fog 



132. To facilitate the extraction of data in English units for current 

 reports, an overprint of black, dotted lines has been made on this 

 form to indicate altitudes in thousands of feet; also, a scale of wind 

 velocities in miles per hour has been added along the bottom of the 

 form. 



133. Form No. 1110-Aer. (table 2) is used for recording the data of 

 two-theodolite observations. Care should be exercised that all data 

 called for thereon are furnished insofar as they are available. It is 

 especially important that the designation, length, and bearing (azi- 

 muth) of the base hne be given; also, the rate of ascent data. Addi- 

 tional instructions regarding the use of this form will be found in 

 section VI. 



134. Form No. 1113-Aer. is used for the tabulation of cloud 

 heights determined during each month. Great care should be exer- 



