TIDES OF CHESAPEAKE BA Y 391 



horses could not remain on the narrow trail through the stormjr 

 night, the sledges were detached and the beasts sent back to the 

 south slope of the divide. 



The snow lay seven feei deep over the stunted willows that 

 grew about the little mountain stream we were following to the 

 Tahltan. This stream was located and a shaft was sunk through 

 the snow and ice to the running water. Pails of water were 

 thrown upon the dry granulated snow in order to get a substan- 

 tial flooring for a single tent. After four hours of work, seven 

 men managed to find shelter from the storm. The draughtsman 

 who had begun to doubt the wisdom of continuing with the 

 party recovered his confidence ; but in this auspicious hour our 

 little sheet-iron stove becoming hot keeled over on its foundation 

 and settled two feet in the snow. This separated the stove pipe 

 at one of its joints, and a dense cloud of smoke filled the once 

 happy home. It was a case of sauve qui pent. Every one fled 

 to the open air ; but above the howling of the storm an over- 

 sensitive ear might now have caught certain lurid epithets and 

 objurgations that only an extraordinary exigency serves to in- 

 voke from the vocabulary of the habitually profane. 



[To be concluded in the November number.] 



TIDES OF CHESAPEAKE BAY « 



By E. D. Preston, 



U. S. Coast and Geodetic Survey 



A successful attempt to fix a permanent tidal plane for the 

 Chesapeake bay has recently been made by the U. S. Coast and 

 Geodetic Survey. During the last fiscal year nearly 40 stations 

 were occupied, at 13 of which we are in possession of simulta- 

 neous tidal observations extending over one complete lunation. 



The application of harmonic analysis to this unique series 

 along our seaboard will open the way for correct predictions 

 from the capes to Havre de Grace, and will also result in the 

 establishment for the whole bay of a plane of reference of un- 

 equaled permanence and undoubted accuracy. The establish- 

 ment of an invariable datum plane is one of the first requisites 

 of inshore hydrography. The accuracy with which such refer- 

 ence level should be determined depends, of course, on the nature 

 of the work based upon it. In foreign surveys vast sums have 



