138 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, NO. 7 
increasing bodily efficiency resulting from the recombinations. But 
if the analysis of the origin of the various animal types just given 
is an approximately true exposition of the facts, the vertebrates, in 
spite of their wonderful complexity of structure and their very high 
degree of efficiency, represent nothing more than the final recombina- 
tion of characters already occurring in the colonial coelenterates which 
were widely dissociated at the inception of bilateral symmetry. 
PROCEEDINGS OF THE ACADEMY AND AFFILIATED 
SOCIETIES 
PHILOSOPHICAL SOCIETY 
877TH MEETING 
The 877th meeting was held in the Cosmos Club Auditorium on Saturday, 
January 27, 1923. The meeting was called to order at 8:15 P.M. by Presi- 
dent Wuite with 29 persons in attendance. 
Mr. G. T. Rupe presented a paper on Instruments and methods for the 
observation of tides. The paper was illustrated with lantern slides, and was 
discussed by Messrs. Lampert, Bowrn, Pautinc, Humpyreys, Hawks- 
wortTH, Faris, LIrrLeHALES, and TUCKERMAN. 
Author’s abstract: A continuous record of the rise and fall of the tide is 
necessary in connection with a number of engineering and scientific problems, 
The simplest method of tidal observation consists in observing the chang- 
ing height of the water as noted on a fixed vertical staff. From this it was 
but a step to devising some mechanical means for recording automatically 
the rising and falling of the surface of the sea. 
The earliest automatic tide gauge of which we have record was devised 
by an English civil engineer, Henry R. Palmer, and is described in the Philo- 
sophical Transactions of the Royal Society, London, for the year 1831. 
Of the automatic tide gauges, two classes may be recognized: (1) those 
in which the changes in elevation are shown in the form of a curve; (2) those 
in which the height of the water at definite intervals is shown by means of 
figures, or the so-called printing gauges. The various forms of the tide 
gauges in use were shown by means of slides and attention called to the 
distinguishing features. : 
Special attention was directed to a new type of automatic tide gauge 
recently developed in the office of the Coast and Geodetic Survey for use of 
hydrographic parties in the field. In designing this instrument the objects 
sought were ease of installation and minimum size commensurate with the 
desired accuracy. The gauge is about 10 inches long and 9 inches high. 
The clock is placed inside the cylinder carrying the cross-section paper on 
which the curve of the tide is drawn. No counterpoise weight is used, a 
coiled spring taking the place of the weight. The float well is ordinary 
34 inch stock iron pipe and in addition to serving as a float, it acts as a sup- 
port for the gauge. No platform is necessary for the installation of this gauge, 
which may be lashed to a pile on a bar or to net stakes in bays or rivers. A 
metallic cover furnishes the only shelter necessary. 
