10 KXI'KIHTIOX TO POINT P.AKROW, ALASKA. 



Wi Kl's method. The outer shelter to be (if wood, lite inner of metal. The observations of 

 minimum thermometers can lie made under various conditions. 



[The shelters furnished consist of an outer wooden louvre work and an inner galvaiii/ed iron 

 shelu r, both framed so as to be easily set up. The minimum temperatures at various altitude* 

 above ground will be observed, and under such various conditions as circumstances sii^-i 



No. lit. The alcohol thermometers ought to be compared at the staiiou of observation with ill,- 

 standard mercurial thermometer at the lowest possible temperatures. 



Xo. L'd. Sea temperatures should be observed, whenever possible, at the surface and at each 

 10 meters (about .'.;:! feet) of depth : as instruments, proper for this observation, the following may 

 be specified: deep sea thermometers, as manufactured or invented by Kkmann ; Xcgretti & /um- 

 bra: Miller-Casella : Jauseii. 



| While at sea the temperature of the surface water will be observed hourly, with the Signal 

 Service water thermometer, by the ordinary methods, and the temperature at each ;!.'! feet of 

 depth, whenever practicable; for greater depths, one of the above deep-sea instruments will bo 

 used.] 



Is'o. 21. The point Centigrade (32 Fahrenheit), for all the. thermometers should be deter- 

 mined from time to time. 



[The testing of thermometers will lie made quarterly, according to the usual Signal Service 

 rules, j 



No. 21'. Piwtiure of Ilir ah: At each station there must be at least two well-compared mer- 

 curial barometers, a reserve barometer, and an aneroid. 



No. 23. The standard barometer ought to be compared or read once each day. 



[Several mercurial and aneroid barometers arc furnished, and all regular observations will bo 

 made from a mercurial barometer, selected from among them, which will be compared, once each 

 day, with the standard barometer. All barometers will be fully compared with the standard once, 

 each mouth ; such comparative readings will be entered on the regular Signal Service forms for 

 this purpose.] 



Xo. 24. Humidity. The psyehrometers (/. e., dry and wet bulb) and hair hygrometer will be 

 used with Regnault's dew-point apparatus as a check, according to Wild's instructions. 



[Comparative readings, with these instruments, will be frequently made and carefully pre- 

 served for future study.] 



Xo. 25. Tin' irind. The wind-vane and Robinson's anemometer are to be read from within 

 the house (seethe method of construction of the apparatus of the Swedish station at Spitsbergen), 

 at the same time ; the force of the wind will be estimated according to the Beaufort scale and the 

 wind-direction to sixteen compass points, referred to the true meridian. 



[The points of the compass on the wind-dial will be adjusted to the true meridian as is ordered 

 for all Signal Service stations ; self-registering instruments of the Signal Service pattern for the 

 velocity and direction of the wind to eight points will be used. A record of wind-force on the 

 I'.eaufort scale (0 to 12), and wind-direction to sixteen points will also be kept and will be 

 entered in the, special column.] 



No. 2G. To aid in deciding the question whether the Robinson's anemometer, with large or 

 with small cups, should be used for determining the force of .storms in the Polar zone, it is rec- 

 ommended that both such be subjected to preliminary experiments. 



[Anemometers of the Signal Service pattern, having small cups and short arms, are the only 

 ones that it is convenient to furnish. For comparative purposes keep two of these in permanent 

 daily use, exposing them in different but good localities. The extra anemometers should be, 

 compared with these during twenty four hours on the first Monday of each mouth, and a full 

 record lie kept of such comparison 



Xo. 27. The clouds. The amount of cloudiness and the direction of the moyement of all 

 clouds should be observed to sixteen compass points. 



[In addition, the kinds of clouds will be noted, and the record kept in the usual Signal 

 Service form.] 



" For Hotci, on special thcniioiiM'tcr.s, luepured for 1hc. Signal Service' .station*. src Section III of these iustvuc- 



ttooi 



