242 Coast Survey of the United States. 
paper, and is assisted in its revolutions by a weight, thus easing 
the labor of the clock. The pencil acts between the two, and the 
intervals of time are noted by a marker connected with a striking 
apparatus. 
In the former tide-gauge, the curves are repeated on the same 
paper—in Mr. Saxton’s a continuous curve is traced from day to 
day. Both machines have reversal scales which can be adapted 
to the variable rise and fall at different places. 
The leading principle in these gauges is the same as in those 
of Lieut. Palmer, published in 1833, and of Mr. Blunt, in 1838. 
The dependence of practice upon theory is well established. 
The contributions of science to meet the daily wants of life, 
constitute her highest claims to respect and encouragement. In 
addition, however, to the useful results to be obtained from the 
researches into the nature of tides upon the shores of the United 
States, the friends of science, in this country, will be gratified to 
see that the superintendent has taken the first step towards rescn- 
ing the nation from the reproach of having hitherto entirely neg- 
lected this important branch of practical astronomy. 
In conclusion it may be mentioned, that with twelve connect- 
ed establishments determined at the office last winter, an attempt 
was made to deduce the place and directicn of the co-tidal line, 
of XII hours upon this coast. 'The formula used by the super- 
intendent was regarded as a means of approximation only, the 
co-efficients being subject to future modification. 
The direction and velocity of tidal currents are now subjected 
to a rigorous investigation. ‘They are determined for the nor- 
mal condition of the tides, and for the effect of occasional de- 
ranging causes, such as winds, &c. The work is laid down upon 
circular and rectangular diagrams, both of them showing the 
courses and rates of motion. When accidental influences are the 
subject of examination, the mean is taken of several days’ ob- 
servations made under suitable circumstances, the temperature of 
the water being always recorded in the note-book. For this 
duty a new hydrographical party is added to the survey. 
Connected with the study of currents is the exploration of the 
Gulf Stream, a work of vast labor and much time, for which the 
preparation is already begun. The magnitude of this task can- 
not be estimated. Its practical and philosophical bearings were 
ably treated by the committee of the scientific convention at 
a 
