486 Effective Scour in Drain-pipes. Presents. [Mar. 28, 



investigation of the behaviour of gases through which electric dis- 

 charges are passing. 



It will be interesting to follow oat the investigation, especially 

 with a view of examining the influence of sun-spot variation. The 

 question of magnetic disturbances is more complicated, but as mag- 

 netical observatories are being established in many countries, the time 

 may not be far distant when we shall be able to bring the irregular 

 disturbances within the reach of calculation. 



In order to facilitate the necessarily long computations, the author 

 makes an appeal to the heads of magnetic observatories to reduce the 

 regular variation according to the method adopted by Wild at 

 St. Petersburg, or that in use at Greenwich, the two being nearly 

 identical. The variations should also be reduced to the geographical 

 coordinates, instead of to magnetic coordinates. 



The author acknowledges the help he has received from Mr. William 

 Ellis in some of the reductions ; he has also to thank his assistant, 

 Mr. A. Stanton, for much labour bestowed on making and checking 

 numerical calculations. 



Y. " On the Conditions for effective Scour in Drain-pipes of 

 Circular Section." By HENRY HENNESSY, F.R.S., Professor 

 of Applied Mathematics and Mechanism in the Royal 

 College of Science for Ireland. Received March 1, 1889. 



Presents, March 28, 1889. 

 Transactions. 



Edinburgh : Royal Society. Proceedings. Vol. XVI. No. 129. 



8vo. Edinburgh 1888. The Society. 



Essex Field Club: The Essex Naturalist. 1888. Nos. 11-12. 8vo. 



Budthurst Hill. The Club. 



Kew : Royal Gardens. Bulletin of Miscellaneous Information. 



No. 27. 8vo. London 1889. The Director. 



Pisa: Societa Toscana di Scienze Naturali. Processi- Verbal i. 



1888. Novembre. 8vo. [Pisa 1889.] The Society. 



Stockholm : Kongl. Svenska Vetenskaps-Akademie. Bihang till 



Handlingar (Afd. 1). Bd. XIII ; Ditto (Afd. 2). Bd. XIII; 



Ditto (Afd. 3). Bd. XIII. 8vo. Stockholm 1888 ; Ofversigt. 



Arg. XLVI. No. 1. 8vo. Stockholm 1889. The Academy. 



Sydney : Linnean Society of New South Wales. Proceedings. 



Vol. III. Part 3. 8vo. Sydney 1888. The Society. 



