TRANSACTIONS OP THE SECTIONS. 115 



On a New Steam-Boiler. By Mr. J. Smith. 



A new and improved safety-lamp was sent for exhibition by Dr. Clanny, but by 

 some error was mislaid till the meeting had separated. 



ADDENDUM TO MATHEMATICS AND PHYSICS. 



m 



On the Abnormal Tides of the Firth of Forth. By Mr. Scott Russell. 



He had on a former occasion presented to the section the result of tidal observations 

 on the Firth of Forth. These observations brought to light the existence of certain 

 very remarkable tidal pheenomena, proving the occurrence on some parts of that Firth, 

 of double tides, or rather perhaps of quadruple tides, being four high waters in each 

 day, instead of only two, as usual. When this subject was formerly discussed, Mr. 

 Russell had attributed these anomalies to the great southern tide-wave entering the 

 Firth at a different period from the great northern tide-wave, to which the periods of 

 high and low water on the east coast of Britain are principally due. But other expla- 

 nations had also been suggested in quarters so high as to entitle them to great respect. 

 For the purpose of settling this question, and, if possible, reducing these anomalous 

 tides to some law, Mr. Russell had recentty instituted a second series of observations 

 on the tides of the Firth of Forth, conducted under very careful observers, the height 

 of the tide being observed simultaneously by different observers, at the different sta- 

 tions, who recorded their observations every five minutes, and continued them uncea- 

 singly night and day. They had only as yet extended over a few weeks, but already 

 there had come out of them results of a decided character, so as to set at rest the 

 question of the origin of these tides, and to illustrate some curious points in the history 

 of littoral tides. The tides already observed had, he thought, proved the accuracy of 

 the theory he had formerly advanced on this subject. But it would still be desirable 

 that these observations should be continued and extended. He then proceeded to ex- 

 hibit the results of the observations in a series of accurate diagrams of the tides. 

 H, H, 



A x X.x 



This diagram represents the two successive tides of a day, as usually observed on 

 the coast of Britain. The line A x, being on the level of a given low water, is divided 

 into equal portions, representing hours, minutes, &c, and lines perpendicular to A x, 

 namely x y, X Y, x y, proportioned to the successive heights, so that H , is high 

 water in the morning, H 2 is high water in the evening, Li and L 2 being the succeed- 

 ing low waters. In this case the tides exhibit the usual form, and at the mouth of 

 the Firth they are in tolerably close accordance with it. In the upper parts of the 

 Firth they deviate from it very widely, as in the following diagram : — 



Hi 



Til f\ Tl; Ho 



A . h l h 



These diagrams exhibit the following changes produced in the tidal course. First 



of all, we have the tide rising to high water at h u falling to a low water at p u 



rising to a second high water at Hi, with a verv small low water at p x , between them ; 



i2 



