54 Royal Society : — Mr. H. T. Brown on the Estimation 



Another fact previously noted by Sir J. Herschel is brought to 

 light — namely, that the time between a minimum and the next maxi- 

 mum is less than that from the maximum to the next minimum. 



Thus the times from the minimum to the maximum are for the 

 three periods 3*06, 4*14, and 3'37, while those from the maximum 

 to the minimum are 6*75, 8'44, and 7'44 years. 



In all the three periods there are times of secondary maxima after 

 the first maximum ; and in order to exhibit this peculiarity, statistics 

 are given of the light-curve of E, Sagittoe and of /3 Lyra 1 ,, two variable 

 stars which present peculiarities similar to the sun. 



Finally, the results are tested to see whether they exhibit any 

 trace of planetary influence ; and for this purpose the conjunctions 

 of Jupiter and Venus, of Venus and Mercury, of Jupiter and Mer- 

 cury, as well as the varying distances of Mercury alone in its ellip- 

 tical orbit, have been made use of; and the united effect is exhibited 

 in the following Table, the unit of spotted area being one-millionth of 

 the sun's visible hemisphere : — 







Excess or Denciency. 





Angular 



Jupiter and 



Venus and 



Mercury alone 



Mercury and 



separation. 



Venus. 



Mercury. 



(Perihelion=0). 



Jupiter. 



to 30 



+ 881 



4-1675 



- 380 



-227 



30 to 60 



- 60 



- 139 



-1188 



-317 



60 to 90 



- 452 



-1665 



-1287 



-594 



90 to 120 



— 5/9 



-2355 



-1262 



-714 



120 to 150 



- 705 



-2318 



-1208 



-508 



150 to 180 



- 759 



-1604 



-1027 



-491 



180 to 210 



- 893 



- 481 



- 519 



-416 



210 to 240 



— 752 



+ 547 



+ 430 



-189 



240 to 270 



- 263 



+ 431 



+ 1082 



- 25 



270 to 300 



+ 70 



+ 228 



+ 1436 



+ 154 



300 to 330 



+ 480 



+ 1318 



+ 1282 



+ 164 



330 to 



+ 1134 



+ 2283 



+ 586 



- 45 



March 17. — Captain Richards, II. N., Vice-President, in the Chair. 



The following communication was read : — 



" On the Estimation of Ammonia in Atmospheric Air." By 

 Horace T. Brown, Esq. 



In the attempts that have been hitherto made to estimate the 

 ammonia present in atmospheric air, the results arrived at by the 

 various experimenters have differed so widely that it is still a matter 

 of uncertainty what the quantity really is. That it is a very small 

 amount all agree, but the extreme results on record vary as much 

 as from 13*5 to '01 part of carbonate of ammonium per 100,000 of 

 air. It may therefore not be without interest to give an account of 

 a simple method affording very concordant and, I believe, accurate 

 results, at the same time being easy of performance and requiring but 

 little time for an experiment. 



The apparatus used consists of two glass tubes, each of about 1 





