348 



Art. XVII. ASTRONOMICAL AND NAUTICAL 

 COLLECTIONS. 



No. XVI. 



i. Description of a New Tide Gauge. 



It is proposed to fix a pipe, with an open mouth, and a triangular 

 orifice (a) at its side, in contact with any convenient part of a 

 bridge or pier that is situated below low-water mark, and to bring 

 from it a pipe, resembling those which are used for the distribution 

 of gas, into any room of a neighbouring house, that may be chosen 

 for the purpose of observation, and there to let it terminate in a 

 well closed reservoir, provided with a little forcing syringe, and 

 with an open barometer gauge, to which a manometrical gauge 

 may be added, if required. 



Immediately before each observation, it will be proper to work 

 the syringe, until the gauge becomes stationary, by the escape of the 

 air under the water, so that the column of compressed air may 

 always begin from the level of the upper angle of the triangular 

 orifice ; the height of the gauge will then obviously indicate the 

 height of the surface of the water above this level. It would only 

 be necessary, if the height of the reservoir above the orifice were 

 considerable, to apply a small correction for the excess of the weight 

 of the air in the pipe, above a similar column of the external air ; 

 this correction being always additive. The gauge might have a 

 double graduation, one for its own height, the other for that of an 

 ecpuivalent column of water. 

 Brighton, 22A Oct. 1823. 



ii. Catalogue of the Orbits of all the Comets hitherto computed. 

 By Dr. Olbers and Professor Schumacher. Astr. Abh. I. 



(Concluded from page ]51 ) 



