| | (chimney pots and slates | | | removed) | 50 10 | Whole gale | Seldom experienced inland; | | | trees uprooted; considerable | | | structural damage occurs | 59 11 | Storm | Very rarely experienced; | | | accompanied by widespread | | | damage | 68 12 | Hurricane | | Above 75 --------+---------------+---------------------------------+----------- The clouds receive more attention at some weather stations than at others. A routine observation consists of noting the kinds of clouds visible, the direction or directions from which they are moving, and the degree of cloudiness--i. e., the extent to which the sky is clouded, stated in tenths, from O = cloudless, to 10 = completely overcast. At many of the more important stations the movements of clouds are observed with a _nephoscope_. The reflecting nephoscope, used in this country, consists of a black mirror in which the image of the moving cloud is watched, the direction of its motion being read off from the graduated circular frame of the mirror. There is also a device for measuring the apparent speed of the cloud. From this the actual speed can be calculated if the height of the cloud is known. There are other nephoscopes, such as Besson’s in which the cloud’s movements are watched directly, and not by reflection. [Illustration: BESSON’S COMB NEPHOSCOPE] The importance of sunshine among the elements of weather and climate is evidenced by the fact that at least two States of the Union, South Dakota and California, contend for the title of “the Sunshine State”--which does not properly belong to either of them. Arizona is the sunniest State of all, and the whole Southwest is sunnier than South Dakota. Devices for registering the duration of sunshine are called _sunshine recorders_. One type (the Campbell-Stokes) works on the burning-glass principle; in others the sun’s rays trace a record on photographic paper. The instrument used by the Weather Bureau consists of an air thermometer having a bulb at each end, one bulb being coated with lampblack. There is a small column of mercury between the two inclosed masses of air. The thermometer is inclosed in a sheath of glass, from which the air is exhausted. When the sun shines on this instrument, the air in the black bulb warms and expands, and the mercury is forced toward the other bulb until it comes in contact with a pair of electrodes, thus closing an electrical circuit. While the circuit is closed, the registering apparatus connected with the instrument makes a step-shaped mark once every minute. When the sun stops shining, the mercury drops back, the circuit is broken, and the recording pen merely traces a straight line.