154 



Report of the Kew Committee. 



II. Meteorological Observations. 



The several self-recording instruments for the continuous registra- 

 tion respectively of Atmospheric Pressure, Temperature, and Humidity, 

 Wind (direction and velocity), Bright Sunshine, and Rain have been 

 maintained in regular operation throughout the year, with the excep- 

 tion of the wet-bulb thermograph. 



The readings of the last-named instrument during the winter of 

 1890-91 became irregular, and it was found to vary considerably from 

 its accompanying standard. It was accordingly decided to dismount the 

 thermometer and to replace it by a new tube, which was done in July 

 last. On examination, the bulb showed the existence of a crack, which 

 eventually extended completely around it. 



The scale value of the new tube has been determined by means of 

 nearly 300 comparative readings, and new glass and ivory tabulating 

 scales for it have been constructed at the Meteorological Office. 



For controlling these values, an experimental determination of the 

 zero of the instrument was made by means of melting ice. 



Experiments were made, unsuccessfully, to use a Richard pen with 

 the Beckley rain gauge, but a BBB black-lead pencil was found to be 

 more reliable in its indications than such a pen. 



The standard eye observations for the control of the automatic 

 records have been duly registered. 



The tabulations of the meteorological traces have been regularly 

 made, and these, as well as copies of the eye observations, with 

 notes of weather, cloud, and sunshine, have been transmitted, as usual, 

 to the Meteorological Office. 



With the sanction of the Meteorological Council, data have been 

 supplied to the Council of the Royal Meteorological Society, the 

 editor of ' Symons's Monthly Meteorological Magazine,' Dr. Rowland, 

 and others. 



Tables of the monthly values of the rainfall and temperature have 

 been regularly sent to the Meteorological Sub-Committee of the 

 Croydon Microscopical and Natural History Club for publication in 

 their Proceedings. Detailed information of ail thunderstorms ob- 

 served in the neighbourhood during the year has been forwarded 

 to the Royal Meteorological Society, soon after their occurrence. 



Atmospheric Electricity. — The electrograph has been maintained in 

 action during the greater portion of the year. The records were, 

 however, lost for forty-eight days on account of the freezing of the 

 water-jet during frost in winter. 



The instrument has failed in sensibility during the last year owing 

 to the large extent of diminution which the 60-cell chloride of silver 

 batterv has experienced in its charge, the potential of which has 

 apparently diminished by one-half. 



