144 Record of the Royal Society. 



cylinder with its spiral strip making in this case a complete revolu- 

 tion for a complete revolution of the wind vane. 



The Lens Room likewise contains an apparatus for examining 

 photographic lenses which was devised by Major L. Darwin (' Roy. 

 .Soc. Proc.,' vol. 52, pp. 403451). 



The parapet of the roof supports two sunshine recorders. One 

 (21) the original "Campbell" pattern, consists of a spherical lens 

 .fitted in a wooden bowl, the intensity of sun light between two 

 successive solstices being measured by the amount of wood charred 

 (' Roy. Soc. Proc.,' vol. 23, pp. 578582). The other recorder (20) 

 is of the modern " Campbell-Stokes " pattern, burning a line in 

 a strip of card-board, which is renewed every evening after 

 sunset. / 



On the roof there is a stand with a camera apparatus (22). By 

 means of this and a similar camera, fixed at a distance of 800 yards 

 from the Observatory, observations were taken some years ago on 

 the height and velocity of clouds (' Roy. Soc. Proc.,' vol. 49, pp. 

 467480). 



THE GARDEN AND ENCLOSURE. (See Plan II.) 



The Magnetic House (1) is a small wooden structure built origi- 

 nally at the cost of General Sabine, once chairman of the Kew 

 Committee. In it absolute observations of the Magnetic Declination, 

 Inclination, and Horizontal Force are taken about once a week. 

 The instruments are of the ordinary " Kew " pattern, the unifilar 

 being by Jones, and the dip circle by Barrow. Observations have 

 been made continuously since 1850. 



Experimental House (2) is a wooden building used for testing self- 

 recording instruments. 



The Workshop (3), and Clinical House (4), are under one roof, the 

 building being substantially built of brick. The Clinical House is 

 devoted to the testing of clinical thermometers, a very large number 

 of which are examined every year. 



An addition (5) has recently been made to the north side of the 

 Clinical House. It is fitted up with a fume closet, resistance box, 

 galvanometer, and other appliances for use in connexion with plati- 

 num resistance thermometers. 



In the centre of the garden are placed the rain gauges. In the 

 Beckley self-recording gauge (6) the funnel empties into a small 

 cistern, floating on mercury, to which a pen is attached. As the 

 cistern fills with water it sinks, carrying with it the pen, which 

 leaves a trace on a sheet of paper wound round a drum driven by 

 clockwork. After a fall of 0'2 inch of rain, the cistern discharges 

 itself by means of a siphon, and rises to its initial position (' Report 



