Synopsis.
The model was constructed to horizontal and vertical scales of 1 : 5,280 and 1 : 115 respectively, and the bed was finished with a layer of cement-sand mortar. Tides were generated by a displacer, moved by mechanism designed on the principle of Lord Kelvin's tide-predicting machine to reproduce the spring/neap cycle. A hump developed on the curve of the rising spring tide in the model at the same level as that on the estuary-tide, becoming more pronounced as the wave advanced upstream. Reclamation of large areas of land on the model caused little increase in range at Glasgow.
Observations taken immediately after stopping the motion of the displacer indicated that the natural period of the model was 4 hours—about one-third of the tidal period. Harmonic analysis of tide curves in the estuary showed that the amplitudes of all the harmonic components increased with distance from the estuary mouth, and that the rate of increase of the third harmonic component was greater than that of the second or fourth. The pronounced hump on the tide curve at Glasgow was caused by magnification of the third harmonic. Analysis indicated that the mean water-level at Glasgow was considerably above that at Gourock.
