378 M. Secchi on Shooting- Stars. 



The apparition of a star was indicated from one place to the 

 other by a touch of the telegraph, given at each place for each 

 star seen ; and when the touches at both places were contempo- 

 raneous, the position as seen from CivitaVecchia was immediately 

 telegraphed to Home, so that we were able to see at once what 

 parallax existed between the two stations. 



The following Table shows the results, relative to the number 

 of meteors, which were obtained : — 









Number of stars observed. 







Date of 

 observa- 

 tion in 

 August. 



Period of observation. 







Propor- 

 tional 

 number 

 per hour. 



Rectified 

 number. 



Contem- 

 pora- 



Non-contempora- 

 neous. 



Com- 













mence- 

 ment. 



End. 



Duration. 



neous. 



At Rome. 



At Civita 

 Vecchia. 









h m 



h m 



h m 













5 



8 48 



10 14 



1 26 



5 



31 



11 



28-9 





6 



8 45 



10 23 



1 38 



12 



38 



8 



306 





7 



9 15 



10 28 



1 13 



8 



43 



3 



41-9 





8 



9 39 



10 37 



58 



20 



34 



21 



558 





9 



9 8 



10 48 



1 40 



19 



53 



19 



43-2 





10 



9 2 



12 5 



3 13 



29 



118 



63 



457 



63 



The moon and mists were somewhat troublesome on the 9th 

 and 10th ; the rectified number expresses the result, in one hour, 

 when moon and mist were both absent. The contemporaneous 

 observations proved, as in 1861, that the parallaxes were, in 

 general, enormous, but nevertheless such as to establish the con- 

 siderable height of our atmosphere. Notwithstanding the inde- 

 termination caused by errors of observation, it was impossible, 

 even for an inexperienced observer, to be deceived, since the 

 parallaxes changed the places of entire constellations. Neverthe- 

 less we shall see that much uncertainty still remains with respect 

 to the distances, and that the solution of the problem is not so 

 simple as is generally believed. 



The determination of the heights of these meteors would be 

 very easy if, in reality, the same point of the trajectory had been 

 observed at the same instant from both stations. For if the 

 two visual rays to this point (say the commencement) were drawn, 

 from their intersection a perpendicular let fall on the plane of 

 the horizon, and the foot of the latter joined to the two stations, 

 a pyramid would be obtained the length of whose vertical edge 

 would be the height of the star. The magnitude of this per- 

 pendicular might be obtained, either from calculation, or by a 

 graphic construction similar to that employed in gnomonics for 

 vertical, declined dials. It is merely necessary to know the azi- 

 muths observed at the two stations, and the angular altitudes. 

 From this construction it follows, too, that the magnitude of the 



