420 Proceedings of the British Association. 



business, to allude to an unintentional omission in his report ; and 

 he stated some important observations of M. Arago, which had 

 not been generally known. 



Dr Robinson read a paper on the visibility of the moon in total 

 eclipses. 



Mr Whewell submitted to the section a paper on collision by Mr 

 Hodgkinson. 



SUB-SECTION. 



M. I. Brunei, Esq. in the Chair. 



Mr Murray gave a description of his apparatus for communica- 

 ting between a stranded vessel and the shore ; with a method of il- 

 luminating by night the path of the arrow and the vessel. 



Mr Addams exhibited a new case of the interferences of sound* 

 produced by waves excited by a tuning-fork in two tubes placed at 

 right angles to each other. 



Mr Dick communicated a description of a new elevated or sus- 

 pension railway, which he proposes to construct, and illustrated the 

 subject by numerous explanatory drawings. 



Mr Brunei exhibited a model, and gave a description, of his new 

 mode of constructing arches. Having explained his plan at the 

 last meeting of the Association, he brought the subject forward on 

 the present occasion merely for the purpose of reporting the results 

 of his subsequent experiments. He stated, that the structure has 

 now stood two winters and two summers, without any sensible 

 alteration; that he is adding to his experimental model, with a 

 view to demonstrate how far it can be extended, not only in the 

 formation of arches, but likewise in other situations, such in parti- 

 cular in the great descents to the Thames Tunnel. 



Mr Whewell exhibited and described a new instrument invent- 

 ed by Mr Saxton, for measuring minute variations of temperature 

 in metal rods, &c. 



A view of the weather, drawn from a register of ten years kept 

 at Edinburgh, was laid on the table by Mr Adie, optician, in 

 which the state of the barometer and thermometer were shown by 

 undulating lines. The depth of rain was shewn on the day in 

 which it fell, by the height of a broad red line ; the thunder storms 

 by a scarlet mark ; the aurora by a blue one ; and part of the space 

 allotted to each day was tinted of a paiticular colour, to represent 

 the direction of the winds, so that the views of the weather for the 

 di£Feront years had only to be compared together, and it could im- 



