EEPORT OF THE SECRETARY. 33 



diurnal and a semi-diurnal, which are exhibited by a diagram and 

 fully analyzed. 



Next, the form of the tide was investigated, and found to occupy 

 a longer time in rising than in falling, or, in other words, its posterior 

 slope i?! more rapid than its anterior — the difference in time is thir- 

 teen minutes at Port Foulke, and fifteen at Van Rensselaer harbor. 



Finally, an investigation is given of the velocity of the tide wave 

 in passing up along Baffin's bay. From this it appears that the crest 

 of high water occupies eight hours in passing from the southern cope 

 of Greenland to Smith's strait, at the head of the bay. From these 

 investigations the velocity of the wave in Davis's straits is 194 statute 

 miles per hour, correspoding to an average depth of 418 fathoms. In 

 Baffin's bay the velocity is 177 miles, corresponding to 349 fathoms. 

 In Smith's strait the velocity is 157 miles per hour, corresponding 

 to 277 fathoms of depth. It may be interesting to state, as one of the 

 results, that the free tide- wave in Davis's strait and Baffin's bay is 

 about 2,300 miles in length, and only 72 feet in height from hollow 

 to crest. 



These statements will serve to give some idea of the complex 

 nature of the investigation of the phenomena of the tides, resulting 

 not alone from the direct action of the moon and sun, but also 

 modified by the superposition of the derived tide of the Atlantic, and 

 by the influence of the configuration of the channels through which 

 the waves are propagated. 



Part fourth gives the observations and discussion of the meteoro- 

 logical investigations. It is divided into three divisions — tempera- 

 tures, atmospheric pressures, and winds — with an appendix giving a 

 record of the weather during the whole voyage, and miscellaneous 

 remarks. 



Port Foulke, the locality of the winter quarters, was in the vicinity 

 of open polar water, which exercises a marked influence on the cli- 

 mate of the region. The comparative mildness of the station is illus- 

 trated by the fact that the simultaneous recorded observations at 

 Port Foulke and Van Rensselaer harbor show that the tempe- 

 rature was 26 degrees lower at the latter than at the former place, 

 though distant only 53 miles. The continuous records at Port Foulke 

 extend over a period of eleven months, and were made at every other 

 even hour, day and night, with a few exceptions, (as to the pressure,) 

 during the whole time. 



The expedition was provided with about two dozen thermometers, 

 consisting of spirit, mercurial, and metallic, of which the index errors 

 3 s 



