Royal Society. 151 



tions. The stream when not diverted by rivers or estuaries appears 

 to run true up and down the channel, and from side to side nearly ; 

 between the Start and Hastings, in the English Channel, scarcely 

 varying a point for nearly five hours ; and in the German Ocean for 

 about four hours ; the varying of the stream there being due, in the 

 author's opinion, to the influence of the Thames and the rivers of 

 Holland. As the stream turns nearly with the high and low water 

 on the shore at Dover, there cannot be nine hours' current in one 

 direction. With regard to the time at which the stream attains its 

 greatest strength, he states that all the observations agree in fixing 

 it at about half-tide (Dover). 



The erroneous impressions above mentioned, the author considers 

 have arisen from the times of the observations when made having 

 been referred to the times of high water at places differing two or 

 three hours from the time of high water at the head of the wave, or 

 from an early popular opinion that the turn of the stream in the 

 offing coincides with the rise and fall of the water on the shore. 



The paper concludes with some remarks on the forms of the tide- 

 wave between Cromarty and the Land's End, which are exhibited in 

 two plans at every hour of the tide, obtained from a combination of 

 the ranges and establishments of Dr. Whewell with those of M. 

 Chazallon ; and attention is particularly drawn to the relative lengths 

 of the stationary wave and the waves by which it is generated ; the 

 former wave being only half the dimensions of the latter. These forms 

 are exhibited on a reduced scale, but much exaggerated in height, 

 and afford a comparison between the curve assumed by the stationary 

 wave and that which the waves would have assumed had they rolled 

 on in an uninterrupted course. 



May 3. — " On the Reduction of the Thermometrical Observa- 

 tions made at the Apartments of the Royal Society from the year 

 1774 to 1781, and from the year 1787 to 184'3." By James Glaisher, 

 Esq. of the Royal Observatory, Greenwich. Communicated by John 

 Lee, Esq., LL.D., F.R.S. &c. 



In this paper the author states that he has examined all the ther- 

 mometrical observations which have been made at the Apartments of 

 the Royal Society, with the view of ascertaining whether the diurnal 

 variations at different epochs were in accordance with those which 

 he had determined from the Greenwich observations, and which are 

 contained in his paper published in the Philosophical Transactions 

 for 1848. The result of this investigation was, that the corrections 

 contained in the tables in his former paper were applicable to the 

 observations of all the years since 1774. 



The author is led from these examinations to the conclusion, — 

 1st, that the instruments used have been uniformly good; 2ndly, 

 that the observations have been faithfully recorded as read from the 

 instruments ; 3rdly, that the readings have been taken with great care 

 with respect to the times stated; and lastly, that the observations 

 were well worth the necessary labour of reduction. He finds, how- 

 ever, that some of the more recent observations of the self-register- 

 ing instruments are liable to some uncertainty. 



