AGRILUS RUFICOLLIS. — FIXED STARS. 119 



NOTE ON AGRILUS RUFICOLLIS. 



BY PROF. 3. S. HALDEMAN, OF COt.UMBIA, PA. 



In its larva state this little insect lives at the expense of the cultiva- 

 ted Rubus (raspberry,) in the heart of which the pupa may be found in 

 the month of May, the perfect insect appearing in June. The larva 

 bores between the wood and bark, injuring the plant and causing a 

 wide unsightly excrescence. It next penetrates to the pith, which it tra- 

 verses for several feet, finally excavating a cavity in which it undergoes 

 its transformations. 



It is probable that the larva feeds during summer and autumn, and 

 passes the winter in the pupa state. The diseased stems are readily re- 

 cognizable, and should be cut out and burnt in autumn or early in the 

 spring. The perfect insect is sometimes found upon Rubus vUlosuSf 

 which renders it probable that this is the natural food of the larva. 



DISTANCES AND MAGNITUDES OF THE FIXED STARS. 



BY DANIEL KtRKWOOn, OF LANCASTER, PA. 



The great problem of determining the distances of the fixed stars, 

 has engaged the attention of the most eminent astronomers for the last 

 two centuries. Supposing them to be suns equal in magnitude to our 

 own, some have endeavored to form an approximate estimate of their 

 distance by photometrical experiments. For this purpose the celebra- 

 ted Iluygens employed a small tube, in one end of which was inserted 

 a spherical lens, so minute that only the 27664lh part of the diameter 

 of the sun's disc could be seen through it. This afforded a light which 

 appeared about equal to that of Sirius ; whence he inferred that that 

 star is 27664 times more distant than the sun. But Dr. Wollaston, by 

 more accurate observations and experiments, found the light of the 

 same star to be to that of the sun in the ratio of 1 to 20,000,000,000. 

 Since, therefore, the light received from a luminous body is inversely as 

 the square of the distance, it follows that the sun would have to be re- 

 moved to 141421 times its actual distance, in order that its light should 

 be no greater than that of Sirius. 



Astronomers, aware that the only true method of finding the dis- 

 tance of a star, is by finding its annual parallax, have devoted much 

 time and labor to this subject. Cassini affirmed that he observed in 

 Arcturus a parallax of seven seconds, and in Capella, one of eight. — 

 This would make the distance of the former 20250 times greater than 

 that of the sun, or 19,2.37,500,000,000 miles. From observations of 

 right ascension and declination, Piazzi made the parallax of Sirius four 



