Prof. Wallace's Geometrical Theorems. 467 



Hence it would appear that high water at London on full and change 

 was at that epoch 2>^ 48", or more than an hour later than at pre- 

 sent. The time of high water at London on full and change is given 

 in Mr. Riddle's Navigation and in other works 2*^ 45"^ ; Flamsteed 

 made it Si^."— pp. 32, 33. 



" It has been remarked, that in consequence of the sheltered si- 

 tuation of the port of London, the great undulations produced by 

 the winds will be less sensible there than on the coasts of France, 

 as at Brest for example. But it should be recollected, that if the 

 tide at London is to be considered as a derived tide, transmitted from 

 the Atlantic, the irregularities which are felt at Brest will equally 

 tend to affect it at all those places which it reaches subsequently. 



" ' During strong north-westerly gales, the tide marks high water 

 earlier in the river Thames than otherwise, and does not give so 

 much water, whilst the ebb-tide runs out later, and marks lower; 

 but, upon the gales abating and the weather moderating, the tides 

 put in and rise much higher, whilst they also run longer before high 

 water is marked, and with more velocity of current, nor do they run 

 out so long or so low.' For this information with respect to the in- 

 fluence of the wind on the tides in the river Thames, I am indebted 

 to Sir J. Hall. 



" It has been found, that since the construction of the new Lon- 

 don Bridge and the removal of the old foundations, there is less 

 water at the St. Katherine Docks at low water by about 18 inches 

 than formerly, but as respects the depth of high water it is the same ; 

 in other words, the flood-tide at the entrance of the St. Katherine 

 Docks lifts about 1 8 inches more within the time of flood than for- 

 merly. I am indebted to Sir J. Hall for this information. I do not 

 however attribute the fluctuations of the establishment to the removal 

 of the old bridge. They began long before the foundations were 

 touched." — pp. 48, 49. 



We hope that the students of exact science may receive many 

 more elementary treatises from the pen of the same distinguished 

 author. 



Geometrical Theorems and Analytical Formula, with their application 

 to the solution of certain geodetical problems, with an Appendix con' 

 taining a description of two copying instruments. By William 

 Wallace, LL.D., Emeritus Professor of Mathematics in the 

 University of Edinburgh ; Fellow of the Royal Society of Edin- 

 1)urgh ; Fellow of the Royal Astronomical Society ; Member of 

 the Cambridge Philosophical Society ; Honorary Member of the 

 Society of Civil Engineers, &c. 155 pp. 8vo. 



The above work is the jjroduction of a man who has been well 

 known to the scientific world for nearly fifty years, and who, in 

 the course of that period, has distinguished himself by excellent 

 treatises on various branches of mathematics in the Encyclopedias, 

 and by original mathematical papers of great merit in the transac- 

 tions of learned societies. It has been written in interesting circum- 

 stances. Several years ago he retired from the active duties of 

 2H2 



