78 Report of the Kew Committee. 



III. SOLAR OBSERVATIONS. 



The sketches of Sun-spots, as seen projected on the photoheliograph 

 screen, have been made on 150 days, in order to continue Schwabe's 

 enumeration, the results being given in Appendix II, Table IV. 



Transit Observations. Regular observations of solar and of sidereal 

 transits have been taken, for the purpose of keeping correct local 

 time at the Observatory, and the clocks and chronometers have been 

 compared daily. 



The clocks, French, Shelton K. 0., Shelton 35, and the chrono- 

 meters Breguet No. 3140, and Arnold 86 are kept carefully rated 

 as time-keepers at the Observatory, and the mean-time clock, Dent 

 2011, lent by the Astronomer-Royal, is also in use in daily com- 

 parisons with the chronometers on trial. 



The chronometer, Molyneux No. 2126, is used as a " hack 

 chronometer " in order to facilitate the inter-comparison of the clocks. 



The scale, figures, &c., on the south meridian mark in. connexion 

 with the transit-instrument having become somewhat obliterated 

 through age and exposure, steps were taken to remedy this defect, 

 and some slight improvements introduced. 



IV. EXPERIMENTAL WORK. 



Photo-nephograph. The past year has been particularly unfavour- 

 able to cloud photography at the Observatory. 



The opportunities of taking negatives of cirrus, to which parti- 

 cular attention is directed, were rare in the earlier months of the 

 summer, and during the later the builders' operations prevented, in a 

 great measure, the work being carried on. 



Several modifications have been introduced into the system of 

 observing, materially simplifying it, and the mathematical treatment 

 of the pictures has also been temporarily set aside in favour of 

 mechanical methods, which afford results of sufficient accuracy in a 

 small fraction of the time occupied by the other plans of reduction 

 which have been employed hitherto. 



Observations of cloud height, drift, and direction have been treated 

 in this manner for 1887 and for 1888, generally with satisfactory 

 results. During April special photographs were taken with one 

 camera only, for showing the structural change in cirrus in short 

 intervals of time, and seven sets of negatives were procured, exhibit- 

 ing the extensive alteration sometimes observed in this class of cloud 

 in a couple of minutes. 



Time Signals. With a view of obtaining the time at the Observa- 

 tory for pendulum work to a high degree of accuracy, and also for 

 comparing daily the time as determined by the Observatory Transit 

 with that distributed by the Postmaster- General from St. Martin's-le- 



