12 NINTH ANNUAL REPORT OF 



as of" so much value to the aboriginal history oi" our continent, and 

 especially in completing the links of civihzation between North and 

 South America, that he prepared a brief memoir upon Zapotec remains, 

 which the Institution has considered it advisable to publish with the 

 drawings. We are happy to believe that this contribution will in some 

 degree supply a deficiency which lias been often acknowledged in 

 regard to remains on the western slopes of the Mexican Cordillera. 



3. Another memoir presented to the Institution is on the Recent secular 

 visifation of the Aurora Borcalis, b}^ Professor Denison Olmsted, of 

 Yale College. This paper partakes more largely of a hypothetical 

 character than most of those which have been accepted for publication. 

 The facts, however, which it contains are considered so important and 

 so well deserving of permanent record, that ihey outweigh this ob- 

 jection. 



On the evening of the 27th of August, 1828, after a long absence of 

 any striking appearances of the aurora boreaUs, there commenced a 

 series of exhibitions which increased in frequency and magnificence for 

 the six following years, arrived at a maximum during the years 

 1835,-'6,-'7, and after that period regularly declined in number and 

 intensity until November, 1848, when, according to the author, the 

 series appeared to come to a close. The occurrence, however, of 

 three remarkable exhibitions of the aurora during September, 1851, 

 and of another of" the first class as late as February, 1852, indicate 

 that the close was not as abrupt as was at first supposed, but still there 

 was a diminution in the number of brilliant exhibitions after 1848. 

 Professor Olmsted, in this memoir, gives the history of the foregoing 

 series of auroras, which, in his opinion, are the most remarkable which 

 have ever occurred since the first recorded observations. The author 

 first refers the several varieties of the aurora to six diflerent forms, viz: 

 1. Auroral light ; 2. Arches ; 3. Streamers ; 4. Coronas ; 5. Waves ; 

 6. Auroral clouds; and afterwards distributes these different forms into 

 four distinct classes. The first is characterized by the presence of" 

 three out of four of tiie most jirominent varieties, viz: arches, stream- 

 ers, coronas, and waves. 



The second class is formed of a combination of two or more of the 

 leading characteristics of" tlie first class. 



The third class consists of" the presence ofonl}^ one of the rarer char- 

 acteristics, either streamers or an arch, or irregular coruscations. 



Class fourth consist^ of the most ordinary form of the aurora, as mere 

 northern twilight or a few streamers. 



From the year 1780 to 1827 striking exhibitions of the aurora were 

 seldom obseived, although, probablv, a greater or less number of the 

 inferior descriptions of those ot' the third and fourth classes occurred 

 every year in our own latitude, and a still greater number in the 

 regions nearer the poles. But aged persons who witnessed the dis- 

 plays of 1827, 1835, 183(), and 1837, testify that they were similar to 

 such as occurred in tlieir youth from 17C0 to 1781. Strange sights were 

 described as having been seen in the air during the old French war, 

 which closed in 1763. From 1781 none of equal intensity had occur- 

 red for nearly half a century ; the splendid arch, therefore, and other 

 striking accompaniments of the aurora of 1827 took us by surprise, and 



