28i HEPORT— 1898. 



which give a very dense image of the sun with a considerable amount of 

 deposit around it. But a local reduction of the image has obviated most 

 of the difficulty. This is effected by applying a weak reducer, in the form 

 of a dilute mixture of hyposulphite of soda and ferricyanide of potassium. 

 The plate is wetted, and when the gelatine is thoroughly moistened the 

 reducer is applied with a paint brush to the parts which are too dense. 

 The image of the sun may thus be brought down to any convenient 

 density without risk of diminishing the value of the plate. It is not easy 

 to effect the reduction without showing some streaks and irregular 

 markings, but for the purpose in view these are of no importance. 



Few measurements have so far been possible in the winter months, 

 not a single opportunity having pi-esented itself during December, January, 

 or February, and very few during November or March. The determina- 

 tions made are, therefore, difficult to compare with those which have been 

 made elsewhere, and of which only the mean value has been published, 

 and it is possible that the greater average altitudes observed may be 

 partly explained by -the absence of observations during these winter 

 months. 



Great altitudes seem especially frequent in hot weather under thunder- 

 storm conditions, in which case the clouds may frequently form at five or 

 six different levels, reaching in some cases to such a height as 80,000 or 

 90,000 feet, which is three times as great as the mean given for the same 

 type of cloud by the International Meteorological Committee in 1894. 



Under similar circumstances around the margins of large thunder 

 depressions clouds of the alto-cumulus and cirro-cumulus types also 

 reach altitudes much greater than the usually accepted means. 



At the same time instances are not wanting in which clouds which 

 cannot be distinguished from those types by their appearance occupy 

 much lower levels. 



Observations made in different months and at different times of day 

 show a well marked rise of the various cloud planes in hotter weather, 

 and an equally well marked rise during the morning and early afternoon. 

 Both phenomena are, as we should expect, considerably varied by the 

 changes in atmospheric pressure, the greatest altitudes having been 

 recorded at the beginning of a barometric fall after a prolonged spell of 

 anticyclonic conditions, while the lowest altitudes seem to accompany or 

 follow a series of cyclonic disturbances. 



There seems reason for suspecting that the high-level clouds reach 

 greater altitudes over the West of England than at other places where 

 observations have been taken, but the variations in the level of a particular 

 type of cloud are so great from week to week, and sometimes even within a 

 single day, that a very prolonged series of determinations ought to be 

 secured before a comparison is made with the researches which have been 

 carried on elsewhere. 



The installation remains in an efficient state, little trouble having 

 been experienced with the electrical arrangements, in spite of the long 

 drought and consequent poor ' earth.' 



The Secretary proposes to continue the work, and if possible to move 

 the whole installation, which is now arranged witli an east and west base 

 line, to some neighbouring site with the line north and south, whereby 

 observations in the early morning and late afternoon will be greatly 

 facilitated. As he is willing to continue to bear the expense no grant is 

 sought, but the Committee ask to be reappointed. 



