TIDES. 



Observations of titles at the United States Itnernational Polar Station, Uglaamie, A laska, 

 were made half-Lourly and uninterruptedly for a period of 112 days, beginning at midnight Febru- 

 ary L'(i, and ending with midnight June 17, 1883. This series, consisting of 5,376 observations, is 

 complete, not a single reading being missed. These observations form a part of the general series 

 of records secured at this station, and were made by the same observers as were the meteorological 

 and magnetic observations. 



Six observers were on duty daily, each making all the observations for four hours. These 

 observers were Charles Ancor, A. C. Dark, J. A. Guzman, J. E. .Maxlield. .John Murdoch, and Middle- 

 tun Smith. How faithfully these observers did their duty may be inferred from the fact that not a 

 single observation was missed. To make a tidal observation, tlieobserver walked out over the level 

 ice to the gauge, about 100 yards from the shore, broke through the ice . : n the hole formed since the 

 last observation, a half-hour before, scooped out the slush so as to clear the line, and then read the 

 scale to the nearest hundredth of a toot. Returning to the house, he wrote down this mutiny, 

 together with the hour, the direction of the icinfl, and the initial of his name. lie further noted 

 whether the tide had turned since the last observation, and if so, the highest or lowest reading 

 reached. This was done by means of a maximum and minimum index, to be described in connec- 

 tion with the gauge. When a maximum or minimum reading occurred between the half-hourly 

 readings, this fact is noted in the record, but is not here reproduced, as it does not appear to much 

 increase the knowledge aiforded by the record as here printed. The record was kept in duplicate, 

 the second or duplicate copy being made daily, and thus kept up with the original. 



Although wind observations were made half -hourly in connection with these tidal observations, 

 nevertheless it is believed that the regular hourly observations of wind and atmospheric pressure 

 will afford all the necessary data for determining the fluctuations of sea-level due to meteorological 

 causes; for these reasons the half-hourly observations are not here printed. 



Gninje. The gauge was constructed at the station in February, l!S<S.'{, and put in position so 

 that observations began on the 20th, as before mentioned. No photograph of the gauge was made, 

 but a drawing to scale, appears on the plate opposite, from which its method of operation will be 

 readily understood. 



KKF is a wooden frame-work standing on the ice over the hole EL A line, L, passes from the 

 'JOO pound anchor through the hole H over pulleys PP, and terminates at the counterpoise ( ' : this 

 counterpoise weighing about L'O pounds. A fixed wooden scale, S. attached to the frame of the 

 gauge, was subdivided to feet and tenths and hundredths, and to the line was attached an index 

 which, moving along the scale, gave readings showing the stage of the tide. 



The zero of the scale was placed low down, and the numbers increased upward and downward 

 from this zero. The numbers above zero were considered positive ( + ) and those below it negative 

 ( ). When the tide rose, the ice, the gauge, and all its appurtenances were lilted up, and in such 

 manner that .the difference between any two index readings would indicate the change of level 

 between the readings. 



From the construction, as well as from observation, therefore, we see that i<re<txi>i(/ numbers 

 indicate rising tide and tlimhiinhiny numbers falling tide. 



In order to record automatically the heights of high and low water, a self registering index 



was adjusts! as follows: 



677 



