APPENDIX A 3t 



the lowest rain gauges at the two stations seems to account 

 for a perceptible difference in the annual rainfall observed. 



Description of the Meteorological Instruments 1 . 



i. A Standard Cistern Barometer, No. 729, by Negretti 

 and Zambra 2 . Examined and certified by J. Glaisher, Esq., 

 F.R.S. Its readings require to be increased by 0-005 inch 

 for index error and capillarity, and further corrected for 

 difference of readings of attached thermometer from 32 by 

 application of corrections for barometers with brass scales 3 . 

 Example of reading with reductions and corrections 

 Barometer 29-998 actual height read off on vernier, 

 f -005 for capillarity. 



for temperature at 57 F. 



29-927 



+ 203 for sea-level 4 . 



30-130 Reduced reading. 



2. Thermometers. 



One sensitive spirit minimum 5 , with forked bulb, 



placed on the grass. 

 One sensitive spirit minimum 5 , with forked bulb, 



placed one foot above it. 



One maximum solar radiation thermometer, with dull 

 black bulb in vacuo, by Casella. In wire cage on 

 the grass before the Laboratory. 

 /One maximum (mercury) ) thermometer, with Phil- 

 (fi\ & JO ne mm i m um (spirit) j lips's index. 



3 j One wet ) bulb thermometer. Fastened in wooden 

 A I One dry j case to wall, with northern aspect. 



1 This description is, in the main, based upon a printed plan drawn up 

 by Mr. Edward Chapman, to whom the arrangement of the register books 

 is also due. 



2 Presented to the Laboratory by Mr. Chapman. 



3 Table of Corrections for Barometers with Brass Scales, by James Glaisher, 

 F.R.S. London: Taylor and Francis, 1856. 



* The cistern of the instrument stood 191-62 feet above sea-level. 

 6 Both made by Casella, and verified at Kew Observatory. 



