514 JOURNAL OF THK WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 21 



the development of an expression for approximate fin eflFectiveness, based 

 upon rather simple mathematics and very convenient in form for engineering 

 use, the essence of this paper being an examination into the magnitude of 

 the errors involved in using this expression without correction, and a deter- 

 mination of the corrections needed for accurate work, a process involving 

 considerable mathematics quite outside the range of usual engine design 

 practice.^ 



855th meeting 



The 855th meeting of the Philosophical Society of Washington was held 

 in the Cosmos Club auditorium, November 5, 1921. It was called to order 

 at 8:15 p.m. by President Paris. 48 persons were present. 



The President called attention to the revised By-laws under which officers 

 of the Society are now nominated and elected. The President announced 

 that the Committee on Elections, consisting of Messrs. C. T. Rude, Chair- 

 man, C. R. Duval, and Irwin G. Priest, was present, and ready to receive 

 nominations in writing for president, two vice-presidents, treasurer, cor- 

 responding secretary, and two members of the General Committee. 



The first paper of the evening, on The great tides in the Bay of Fundy , and 

 their causes, was presented by Mr. H. A. MarmER, and was illustrated. It 

 was discussed by Messrs. Crittenden, Priest, L. J. Briggs, White, and 

 Stimson. 



In the Bay of Fundy here occurs the greatest known rise and fall of the 

 tide. In the upper part of this bay, in a period of six hours, the tide rises 

 a vertical distance of from 40 to 50 feet, and in the following period of six 

 hours it falls the same distance. 



The Bay of Fundy is a funnel-shaped body of water with a gradually 

 shoaling bottom from mouth to head, and it is to these features that the 

 great range of the tide in the upper reaches of the bay has been ascribed, 

 for it is well known that the concentration of the energy of motion of a large 

 mass of water in a narrowing channel brings about an increase in the range 

 of the tide. But this explanation does not account satisfactorily for an in- 

 crease in the range from less than 10 feet at the mouth to more than 40 feet 

 at the head. 



On the southern shore of the bay the range of the tide increases from 9.1 

 feet at Cape Sable to 44.2 feet in Noel Bay. On the northern shore a sim- 

 ilar condition prevails, the range of the tide increasing from mouth to head, 

 and this increase becomes even more striking if one begins with the tide at 

 Nantucket Island and goes up the coasts of Massachusetts, New Hampshire, 

 Maine, and New Brunswick, which form the western and northern shores 

 of the Gulf of Maine and the Bay of Fundy, the mean range at Nantucket 

 being a little more than one foot and at Moncton 41.2 feet. 



An examination of the ranges of the tide on the two shores of the bay brings 

 out the fact that on the southern shore the range of the tide is greater than 

 on the northern shore, this difference being due to the deflecting force aris- 

 ing from the rotation of #ie earth. 



From a study of the times of the tide in the bay and of the relation of time 

 of current to time of tide it develops that the tidal movement is of the sta- 

 tionary wave type, with the node at the mouth. In consequence of this 



'See also the paper by the same authors in this Journal 11: 409^16. October 19, 

 1921. 



