The nephoscope may be placed on a table, out of doors in fine weather, or close to a window from which the clouds to be observed can be seen. The instrument must be properly oriented, so that the four points marked N., E., S., and W. on the frame shall correspond to the four chief compass directions. The zero (0°) of the movable brass scale is usually put at the S. Hence, if a cloud is found moving from exactly SW., the angular measurement of its direction of motion will be 45°. If a cloud is moving from due E., the angular measurement of its direction of motion will be 270°. When the sky is completely overcast with a uniform layer of cloud, it is usually impossible to determine any direction of movement, because of the difficulty of selecting and keeping in view, on the mirror, some particular point of cloud. Observations with the nephoscope may be made as often as is desired, and should be entered in an appropriate column in the record book. =Tabulation of Observations.=——A convenient form of table which may be used in the complete instrumental observations is given on the next page. The number of columns and their arrangement may, of course, be varied to suit the number and the nature of the records. =Summary of Observations.=——In the preceding chapter we have seen how to obtain the mean monthly temperature from the daily observations, the frequency of the different wind directions for each month, and the total monthly precipitation. The addition of the new instruments, the maximum and minimum thermometers, the psychrometer, the anemometer, and the nephoscope, enables us to obtain the following additional data in our monthly summaries. _Temperature._——The _mean monthly temperature_ may be obtained from the maximum and minimum temperatures as follows: Add together all the daily maximum and minimum temperatures for a month. Divide this sum by the total number of readings you have made of each thermometer (_i.e._, one reading of the maximum and one of the minimum each day, making two readings a day), and the result will be the _mean monthly temperature_ derived from the maximum and minimum temperature. This is a more accurate mean temperature than the one noted in the summary of the preceding chapter. Add together all the maximum temperatures noted during one month. Divide this sum by the number of observations, and the result gives the _mean maximum temperature_ for the month. TABLE FOR METEOROLOGICAL RECORD.