380 ANNUAL OF SCIENTIFIC DISCOVERY. 



able for the periodical displays of luminous meteors, as November and August 

 9th to 14th days, Mr. Greg observed that the number of aerolites recorded as 

 falling on those days is remarkably small, indeed under the average of the 

 year, for out of 155 falls (the day as well as month of fall being known), but 

 four have fallen between the 9th and 14th days of August and November. 

 The aerolitic and (luminous) meteoric epochs also would appear to differ, with 

 the exception of the 29th of November. From this circumstance it seems 

 probable that aerolites, and the majority of luminous meteors (especially pe- 

 riodic and conformable ones), are resolvable into separate classes; and in 

 corroboration of this it may be mentioned, that while the number of aerolites 

 whose falls have been recorded are about equally divided for the first as for 

 the second half of the year, this is very far from being the case with luminous 

 meteors, by far the larger numbers of which are observed during the second 

 half of the year, viz., from July to December. While, then, we consider 

 aerolites as belonging to asteroids, with orbits superior to the earth's, and par- 

 taking of the nature of true though minute planets, the majority of luminous 

 meteors may be considered as having characters more in common with 

 comets. It has been shown by several astronomers, as Olmstead, Pierce, 

 Erman, and others, that the majority of periodic meteors have orbits inferior 

 to the earth's, and their perihelia near the planet Mercury. Mr. Greg con- 

 cluded, after making some observations in favor of the self-luminosity of 

 meteors, by suggesting the probability of their having a nature less dense 

 than that of aerolites, but denser than that of comets, and that it is not 

 improbable that they have a fluid or viscid nature. 



ASTRONOMICAL MEMORANDA. 



At a recent meeting of the American Academy, Mr. G. P. Bond stated that 

 he had found that the horizontality of the axis of the great equatorial at Cam- 

 bridge is subject to a regular disturbance, its position going through a succes- 

 sion of changes almost uniform every year. This he ascribed to the unequal 

 action of temperature upon the two supporting pillars. The western pier 

 rises from March to September, and is depressed during the remainder of the 

 year. Mr. Bond exhibited a diagram, showing by a series of curves the rate 

 of elevation and depression through different months, for the past five years. 

 The amount of departure from a horizontal position is y^ 1 ^ of an inch in all. 



Mr. Bond also said that he had been making some investigations to ascer- 

 tain whether the attraction of the moon has any effect on the motion of a 

 pendulum, and consequently upon the rate of a clock. He had found this last 

 to be changed to the amount of j-^^ of a second daily. At the equator the 

 moon's attraction changes the weight of a body only T^QIJ-O o o" ^ * ue w ^^ e > 

 yet this force is sufficient to produce the vast phenomena of the tides. 



DR. KANE'S OBSERVATIONS ON ARCTIC TEMPERATURES. 



On the 17th of January, our thermometer stood at 49 below zero; on the 

 20th, the range of those at the observatory was at 64 to 67. The tempera- 

 ture at the floes was always somewhat higher than at the island ; the differ- 



