12 KXI'KDJTIOX TO POINT UAKKOW, ALASKA. 



Nil. 38. Tne accuracy of the magnetic observations should hi' surli as to give (lie declination to 

 the nearest minute and the horizontal and vertical intensity in units of (lie t'ourtU decimal place. 



No. .'!!>. On the term da\s. observations ol' auroras are also to be made continuously. More- 

 over, auroras are also to lie observed from hour to hour throughout the .period of magnetic observa- 

 tions, and especially in reference to their form and momentary position in altitude and true azimuth. 

 The intensity of the light is to be estimated on a scale of 1. :_', :i, 4. 



Xo. 40. Isolated auroral phenomena must be made the subject of thorough observations in 

 connection with which the various phases are to be noted simultaneously with readings of tho 

 magnetic variations instruments. 



[Those of the party not. engaged at the magnetic instruments will observe and record auroral 

 phenomena.] 



No. 11. Since the greatest possible simultaneity in the readings is a point of the highest impor- 

 tance, the determinations of the location and of the time are to be made with instruments having 

 firm foundations (such as the universal instrument or astronomical theodolite, the vertical circle, 

 zenith telescope, astronomical transit, &c.) ; this, however, does not exclude the use of reflecting 

 instruments of a superior class. By all means, therefore, must efforts be made to determine the 

 geographical position, and especially the longitude of the station, as soon as possible after it has 

 been occupied. 



[The first approximate longitude of the station, as determined by chronometers, will be checked 

 as frequently as possible by lunar distances, occultations, &c., and the value adopted in the daily 

 work of the station will be revised as often as necessary, preferably at the end of each ijuarter. 

 The details of the magnetic observations will be regulated according to the instructions published. 

 by the Superintendent of the United States Coast and Geodetic Survey.] 



,'j. ELECTIVE OBSERVATIONS. 



"No. 42. The Conference recommends the following observations and investigations most earn- 

 estly to the consideration of all those to whom is intrusted the preparation of instructions for an 

 expedition or who themselves are, assigned to such work. 



No. 43. Meteorological. The diminution of temperature with altitude, the temperature of the 

 earth, of the snow, and of the ice at the different depths should be determined. 



[The forms of the snow-crystals should be recorded by careful drawings ; the amount of hoar- 

 frost accumulated on some well-exposed object should be measured by the use of the scales fur- 

 nished by the medical department. Apparatus is ordered to be provided for the preservation of 

 air and of air-dust for future analysis.] 



Xo. -14. Observations of insolation (or solar radiation) are to be made,, as well as observations 

 on spontaneous evaporation, which latter can be made during the winter by weighing cubes of ice, 

 and during the summer by the evaporimeters. 



[A shallow circular vessel of water, whether fluid or frozen, exposed to the open air and sun- 

 shine, should have its loss of weight determined, daily or oftener, by delicate scales. | 



Xo. 45. Mai/nctiatl. From time to time absolute simultaneous readings of all three elements 

 of terrestrial magnetism must be made in order to accurately determine the ratio between the 

 {simultaneous changes of the horizontal and those of vertical intensity. 



No. 40. Qaleanic earth currents. Observations are desired of earth currents in intimate con- 

 nection with magnetic observations and the auroral phenomena. 



[Telegraph lines of well-insulated wire, extending a short distance north and south and also 

 east and west, and furnished with resistance coils and detection needles, are supplied, and 

 every effort should be made to carry out these observations.! 



Xo. 47. Jlydniyraphir inrt.-lnjut'wns. Observations of the direction and strength of the ocean 

 currents and the movements of the ice. 



No. 4.s. Jtiri'nin xMtndini/M and observations upon the physical properties of the sea water, for 

 instance, determination of the temperature, specific density, gaseous contents. &c.. and these 

 objects sliould be especially kept in view in the selection of a vessel for the expedition. Observa- 

 tions on tides, when possible, should be made with the self-registering apparatus. 



