154 



SCIENCE. 



The shower was observed by the writer this year on 

 the evenings of the 8th and 9th (the sky being unfor- 

 tunately overcast on the 10th and nth), and the dis- 

 play found to be a feeble one. 



A three-hours' watch on the 8th, from 9 to 12I1., 

 revealed 37 meteors. Of these, 16 were Perseids, 

 giving as an hourly rate of Perseids (allowing for time 

 spent in registering such tracks as were well observed) 

 6, and for all meteors 14. 



The following table shows the number of meteors 

 recorded each hour on the 8th during the watch, and 

 also the calculated horary number for one observer 

 looking towards the East: 



Duration 



u 







Calculated 







rt 



E 







State 



of 



1* 



v 





Horary No. 















of 



Watch. 





m 











C 



*o 



1 



All 



Perseids. 



Sky. 









From 



To 



J 



a 



&. 



Meteors. 







h. m. 

 9 



h. m. 



10 



h. 



1 



9 



6 



10 



7 



Very 



10 



11 



1 



11 



3 



13 



4 



Clear. 



11 



12 



1 



r 7 



7 



20 



8 





9 



i2h. 



3h. 



37 



16 



'4 



6 





The magnitude of those recorded were as follows : 



= y > iMag.*— iMag. = 2Mag.=3Mag. = 4 and fainter. Total. 

 Perseids... i i 362 3 = 16 



Others o o 246 9 = 21 



Total.... 1 



37 



The radiant point of the Perseids was deduced as 

 at R. A. 38° + 56 . Two showers in Cepheus furnished 

 the majority of the uncorformable meteors recorded, 

 their deduced positions being at R. A. 5°+75° and 

 R. A, 332°+6o . The evening of the 9th was generally 

 clear (a few clouds at times but slightly interfering 

 with the observations), and a watch of four hours, 

 from 9 to 13L, was sustained, 91 meteors being re- 

 corded. Of these, 54 or 59.4 per cent, were Per- 

 seids, 12 or 13 per cent. Cassiopeids, and 25 or 27.3 

 per cent, belonged to feebler showers in Andromeda, 

 etc. 



The number recorded each half hour, and the cal- 

 culated horary number, were as follows : 



Duration 















Calculated 



State 



of 







V 



u ■ 



(A 



c/i 



."2 



V 



0. 



.2 



3 



Horary No. 



of 



Watch. 











X. 



be 



c 



O 



I 



All 



Perseids. 



Sky. 









From 



To 



J 



55 



a. 



Meteors. 







h. m. 



h. m. 



m. 















9 



9 30 



30 



9 



5 



2 



22 



12 



Clear. 



9 3° 



10 • 



u 



10 



8 







*4 



«9 





10 



10 30 



ti 



10 



6 



3 



25 



'4 



FewCTds. 



10 30 



11 



11 



'" 



11 



7 



2 



26 



16 



Clear. 



11 30 



" 



'4 



10 



2 



35 



23 



FewCl'ds. 



11 30 



12 





'5 



7 



2 



37 



16 





12 



12 30 



" 



11 



5 



1 



26 



12 



Clear. 



12 30 



13 





11 



6 



O 



26 



14 





9 



• 3h. 



4 h. 



91 



54 



12 



28 



16 





Meteors thus appeared thickest between n and 

 i2h., when the hourly rate for all meteors was about 

 36, and of Perseids 20. The shower in Cassiopeia 

 appears of considerable intensity, and probably the 



confounding of these meteors (Cassiopeids) with the 

 true Perseids (the two radiants lying approximately 

 near one another) may account for the large hourly 

 rate of meteors being recorded as belonging to the 

 Perseids by ordinary and occasional observers not dis- 

 criminating enough, or who are not aware that two 

 distinct showers exist in this region of the sky. The 

 magnitude of those recorded on the 9th were as 

 follows : 



~ If or 3 > iMag.* = iMag. = 2Mag. = 3Mag. = 4 and fainter. Total. 

 Perseids... 4 5 8 13 9 15 = 54 



Others 1 o 4 27 23 = 37 



Total s 5 12 15 16 38 — 91 



The radiant point of the main Perseid stream was 

 very accurately deduced from several very short tracks 

 near the focus, and from one perfectly stationary me- 

 teor of the 1st mag., visible two seconds and very ex- 

 actly noted, as at R. A. 44^° + 56X°. A secondary 

 Perseid radiant was reduced from a few short tracks, 

 and one very nearly stationary meteor, as at R. A. 

 55°+ 57°- Among the bright meteors recorded was 

 one at i2h. 55m., which equalled $ (Venus) in 

 brightness, and was of a blue color, with path from 

 R. A. 26o°+67j£° to 212° + 66°. This meteor came from 

 the direction of Cygnus. A letter received from Mr. 

 W. F. Denning, F. R. A. S., of Bristol, England, in- 

 forms the writer that the shower was well observed in 

 England. Mr. Denning at Bristol recorded from 

 August 6 to 13, inclusive, 419 t during a period of 

 i6£h. watching, and of these 240 were Perseids. He 

 found the hourly rate of all meteors on the 9th to be 

 44, and of Perseids 28. On the 10th (when it was 

 foggy) 34 and 28, respectively. The radiant point 

 appeared to shift in R. A. (increasing) every night, 

 for while on August 6 it was at R. A. 38° + 56° and Au- 

 gust 7-8 at R. A. 4i°+55°, it was at R. A. 48° + 57° on 

 August n-12, and at R. A. 49 l A° + S7%° on August 

 13 th. The meteors were also successfully observed 

 at the Royal Observatory, Greenwich, where the greatest 

 hourly number on the 10th was determined to be 

 about 25, and also by Major Tupman, Mr. Corder, 

 and other prominent observers. 

 Cambridgeport, Sept. 12, 1880. 



AMERICAN ASSOCIATION FOR THE AD- 

 VANCEMENT OF SCIENCE, 1880. 



(Continuation 0/ papers read.) 



NOTES ON JAPANESE PULMONIFERA. 

 By Prof. Edw. S. Morse. 



In this communicetion Mr. Morse called attention to the 

 occurrence of a number of species of land snails in Yeso, 

 identical with forms occurring in New England. 



He also showed the occurrence of two species of slugs 

 in Japan, which are also common in New England. 



While he had met with most of the fresh water genera of 

 Pulmonifera in Japan, he had never yet found an example 

 of Physa. 



PROBLEMS IN WATSON'S CO-ORDINATES. 



By Thomas Hill, D.D., LL.D. 



In this paper Dr. Hill investigates the equation p=A(a — 

 hSin. mv) n ;givinghis principal attention in tin- case in which 

 b=m = i, and n= — i, which represents a curve like a figure 



8 with its top concave, somewhat like the sign for Taurus. 

 When a=o, this becomes a parabola; and when a>2, an 





