EXPEDITION TOWARD THE NORTH POLE. 371 



parntns can bo carried across the ice barrier, tlie boat party sliould be 

 provided ^Yitll 1,000 fathoms of small twiue, marked in lengths of 10 

 fathoms. Stones taken on board when the boat is launched, may serve 

 as weights. 



Bottom should be brought up whenever practicable, and specimens 

 preserved. Circumstances of time and opportunity must determiue 

 whether a dredge can be used, or merely a spccimen-cvp. 



Temperature of the sea should be observed with the " Miller protect- 

 ed bulb thermometer," made by Casella, near the surface, about two 

 fathoms below the surface, and near the bottom. When time permits, 

 observations at an intermediate depth should be taken. These observa- 

 tions have a particular bearing on the general circulation of the ocean, 

 and are of great imi)ortance. 



Tides. — Observations of high and low water, as to time and height, 

 should be made continuously at winter quarters. The method adopted 

 by Dr. Hayes is recommended. It consists of a graduated stall an- 

 chored to the bottom, directly under the " ice-hole," by a mushroom- 

 anchor, or heavy stone and a chain, which is kept stretched by a counter- 

 weight attached to a rope that passes over a pully rigged overhead. 

 The readings are tiiken by the height of the water in the '" ice-hole." 

 In the course of a few days' careful observations the periods of high 

 and low water will become sut!iciently well known to predict the turns 

 api)roximating from day to day, and subsequently, observations taken 

 every five minutes for half an hour, about the anticipated turn, will 

 suffice, provided they be continued until the turn of the tide has be- 

 come well marked. 



Tidal observations taken at other points, when a halt is made for 

 some time, even if continued not longer than a week, will be of special 

 value, as affording an indication as to the direction in which the tide- 

 wave is progi^essiug, andinferentially as to the proximity of an open sea. 

 If, as the expedition proceeds, the tide is found to be later, the iudica- 

 tion is that the open sea is far distant, if indeed the channel be not 

 closed. But if the tide occurs earlier, as the ship advances, the proba- 

 bility is strongly in favor of* the near approach to an open, deep sea, 

 communicating directly with the Atlantic Ocean. 



In making such fi com]>arison, attention must be paid to the semi- 

 monthly inequality in the time of high v>ater, which may be a-pproxi- 

 mately taken from the observations at winter quarters. Observations 

 made at the same age of the moon, in difi'erent places, may be directly 

 compared. 



When the water is open, the tide may be observed by means of a 

 graduated pole stuck into the bottom; or, if that cannot be conveniently 

 done, by means of a marked line, anchored to the bottom, and floated 

 by a light buoy, the observation being taken by hauling up the line 

 taut over the anchor. 



Currents. — It is extremely desirable to obtain some idea of the cur- 



