520 REPORT—1890. 
effect of tides in the generators diverging from the simple harmonic tides 
so far used, simple harmonic tides being the exception at the mouths of 
actual estuaries. It would also be desirable before concluding these 
experiments that they should include the comparative effects of tides 
varying from spring to neap. 
§ III.—Morirications or THE APPARATUS. 
16, General Working of the Apparatus—The apparatus has worked 
perfectly in all respects except that of the driving cord connecting the 
water motor with the gearing. For this cord hemp was first used, as it 
was liable to be wet. This hemp cord wore out with inconvenient 
rapidity. A continuous cord made of soft indiarubber was then tried, 
and, after several attempts, has been made toanswer well. The only other 
failure was the small pinion, which was fairly worn out, and had to be 
replaced. 
17. Extensions.—F¥or carrying out the experiments on the V-shaped 
estuaries the original tanks had to be increased in length. To do this it 
was necessary to remove temporarily part of the glass partition dividing 
the engine room of the laboratory, in which the tanks are placed from 
the testing room. This being done, the tanks were then extended, as 
shown in Plate I., the first extension being an addition of a trough 6 feet 
long and 2 feet wide to Tank A, and a similar extension of half the 
size to Tank B, the new tanks being thence called C and D. 
18. Extensions for Tidal Rivers.—The second extension consisted of a 
trough 19 feet long and a foot wide to the end of C, the new tank being 
thence called KE. The corresponding extension to D was not at first made 
in the same way, because to do so would require the removal not only of 
a panel of the glass partition, but also of a fixed bench, which was a 
much more serious matter, or else the extension would have closed up an 
important passage. The extension was therefore made, as shown in Plate 
XVII., which admitted of the tidal river being the corresponding length 
to that in E, but required a bend of 180°, which was effected by two sharp 
corners. This tank was thence called F’. This was the best that could 
be done during the time the students were in the laboratory. It was not 
certain that the corners would produce any sensible effect, whereas if the 
results obtained in F’ were not similar to those in E no time would have 
been lost, since the straight extension could not be made till the end of 
June. As the results in FE’ were not similar to those in E in a way 
which might be explained by the bends, as soon as possible the straight 
extension was made similar to EH, and the tank called F. 
All these tanks were constructed in the same manner as the original 
tanks, and covered with glass at the same level as A and B, under which 
glass survey lines, conforming to those on A and B, were set out. 
19. The Numbering of the Cross Section.—The extension of the tanks 
raised the question as to how the new cross sections should be numbered : 
the numbering of A and B ran from the ends of the tanks, and it seemed 
best to run the numbers in © and D from the ends of these tanks, con- 
tinuing this new numbering to the generators. On the other hand, as 
the long, narrow extensions in E and F were more in the nature of a tidal 
river than an estuary, the numbers in these were carried backwards 1, 
&c., from the ends of C and D, in which the cross sections preserved the 
saine numbers as before. 
