C164 Proceedings (jf'the British Association. 



20. Mr Baily read his report on the Aberdeen standard scale 

 of 8 feet, which was compared with that of the Astronomical 

 Society, by the recommendation of the Association. He found 

 a small difference, and concluded with some suggestions for the 

 better construction of such scales. Sir Thomas Brisbane re- 

 marked the necessity of attending to expansion. Professor Ste- 

 velly made some observations on the same point, to which Mr 

 Baily replied, by stating the precautions which had been used. 



21. Mr Snow Harris on Thermometric Observations. He pro- 

 duced a report of hourly observations, conducted at Plymouth, 

 and illustrated it by diagrams, representing the mean daily 

 curves of temperature at different periods of the year. He com- 

 pared them with similar observations made at Leith. 



22. Mr G. Jerrard On the Solution of Algebraic Equations. 

 An account of these researches was given by Professor Hamil- 

 ton. 



23. Professor Phillips presented the third report on the fall 

 ef rain, in continuation of his former reports. It fully confirm- 

 ed his remarkable results announced last year to the Association, 

 xm. that less rain falls, in proportion to the height from the 

 ground ; and extended them so as to lead to some general theo- 

 retical views. Mr Phillips proposed that the Association should 

 either provide, or recommend members to procure rain-gauges, 

 and have them placed at different places, at different heights 

 from the ground, not to exceed 150 feet, which he appeared to 

 think quite sufficient for the collection of data, to enable calcu- 

 lations to be made to ascertain the quantity of rain which would 

 fall into a gauge at any height. This suggestion led to some 

 discussion in relation to the dew which would be collected in the 

 gauge along with the rain> and thus would vitiate the result. It 

 was also stated, that radiation from different places had a great 

 influence on the formation of vapour. Thus, the Sugar-loaf and 

 Kowth mountains are frequently capped with clouds, when the 

 Dublin mountains are quite clear ; hence the necessity of care 

 being taken in placing the gauges. It was also stated, that 

 there is a quantity of rain discharged from a variety of those 

 i-Iouds known by the name of nimbus, which never extends to 

 within a considerable distance of the ground. These clouds, 

 which do not extend to the ground, are well known. The rain 



