KXI'KIMTION TO I'OINT 15AKKOW, ALASKA. 13 



[With regard to tidal observations, tin- instructions published by (lit- tinted Stiit. .mil 



Geodetic .Survey arc to be followed. Class-stoppered bottles are provided lor preseniu;; >pcei- 

 incus of sea water to be brought back for examination. 



No. 49. ParaUux of the aurora. Determination should lie made of the altitude, of the aui.ua 

 by means of measurements made for example with the meteorograph, which must be made by small 

 detached parties of observation, having also, if possible, one party observing simultaneously the 

 variations of magnetic declination. 



[Particular attention will be paid to determining the apparent position in altitude and a/imuth 

 of bright meteors and shooting stars and of definite portions of the aurora borealis, and to draw- 

 ings of the appearances presented by the phenomena, as seen by observers situated as far apart 

 (say one-half to five miles) as possible; in these drawings the auroral phenomena should appear 

 in their proper positions relatively to the horizon, meridian, fixed stars. &e.. and to that cud each 

 member of the party, without exception, will learn the names and configurations of the stars 

 shown upon the map of stars furnished yon. A supply of these maps is furnished, suflieient to 

 allow of using them as base charts upon which to enter the observed phenomena in special <.. 

 Attention is called to the points of inquiry suggested in the Annual Report of the Chief Signal 

 Officer, 187G, pp. 301-335.] 



Xo. 50. Observations of, 1, atmospheric electricity; 2, astronomical and terrestrial refractions; 

 3, length of the simple second's pendulum ; 4, observations on the formation and growth of floating 

 ice and glaciers. 



[Attention is called to the observations on the formation of ice made by Nares and other 

 explorers. The pendulum observations will be made in accordance with special Coast Survey 

 instructions.] 



No. 51. Observations and collections in the realms of zoology, botany, geology, &c. 



[The instructions given by Prof. Spencer F. Jtaird to the naturalist will he followed by him.] 



Xo. 52. There will also be made special observations relating to the whole polar problem, such 

 as the flight of birds, presence of drift-wood, and from what direction it came, and other matters 

 as may suggest themselves from time to time and be found practicable. 



III. SPECIAL INSTRUCTIONS RELATIVE TO CARE AND USE OF SPECIAL TIII.IJAIUMI.] i;i:s. 



See |>ai'iii;r;i|>li IV. ]>;.<> 10.] 



The construction of the minimum standard thermometers designed for the Arctic Motions 

 having been intrusted to the Thermomctric Bureau of the Winchester Observatory of Vale Col- 

 lege, the astronomer in charge of that institution furnishes the following special instruct; 

 which will be carefully followed: 



HA-VTN, Mnij ;]<>. issi. 



" GENERAL R KM ARKS AND DIRECTIONS < '< INI 'KliNIN^ THE SIiiNAI. SERVICE MINIMfM STAND- 



ARDS, NOS. 1 TO 12 iNCi.rsm;. <-<'\sn;rrTi;i> \\\ THE WINCHESTER oi:si:i;\ AT<H;V OF 



YALE COLLEGE. J. AND II. ,T. (iKEEN. MKi'HANK'IANS. 



''Material*. The alcohol, carbon di-sulphide, and ethyl oxide u,-ed are as pure as the chemical 

 processes will admit. For thermometric purposes they may be assumed < hcmieally pure. There 

 is no more air above the liquid columns than is accidentally admitted in the p; sealing 



the tubes. In this respect these standards are different from the ordinary spirit thermomei 

 It is probable that the great purity of the alcohol will render it nearly as valuable for temper- 

 atures below 80 Fahrenheit as the carbon and ether thcrmomc, 



' 1'Hm-t ions for <-an-iai/f. It is highly desirable that these thermometers should be kept, as 

 ni-arly as possible, in the Manic condition as on leaving the observatory. For this pnrpoM- they 

 have been carefully packed in a vertical position, and care must be taken to see that they a:. 

 repacked, with the bulb down. Owing to the low boiling points of the ether and caibou di-sul- 

 phide they are not (probably) accurate at temperatures above + 60 Fahrenheit, but they will 

 remain clear and limpid at temperatures below x.cro, at which the alcohol tlicrmometcis may (but 



