This chart is divided vertically into thirteen months in order to include the first month of the following yean Each month is further divided, 

 bythe lighter lines, into periods of six day^ each, except in the case of those months having fewer or more days than 30, when the last division 

 of the^month may equal four, five, or seven days. The ist, 6th, 12th, i8th, 24th and last days of the' month fall on the vertical lines.. The 

 transverse lines represent the stations from which^they extend, A complete break in the isothermal line' opposite; any;"station generally indicate* 

 that the temperature did aot reach the isotherm at that station' during the year. A. line consisting' of dashes den.Qtes a lack of^obsecyations' for 

 the corresponding station. 



