G. NATURAL HISTORY AND ZOOLOGY. 325 



servations were made on every week-day during a month. 

 It was found that on the first day the observations were scat- 

 tered through a very large range of error, the difference in 

 time between the records of the event and of the observation 

 varying in fact between the extreme values from 0.16 to 0.98 

 of a second. The personal equation proper on the second day 

 was between 0.2 and 0.3 of a second, and from that time it 

 steadily decreased until it amounted only to one seventh of 

 a second ; it then gradually increased until the twelfth day, 

 when it amounted to 0.22 of a second. While this variation 

 in personal equation occurred, the range of errors or discord- 

 ances was constantly decreasing, until on the twenty-fourth 

 day the probable error of the result does not exceed one 

 eightieth of a second. This is considered to clearly demon- 

 strate the value of such practice in training the nerves for 

 observation ; and he recommends that transit observers be 

 kept in constant training by means of similar observation of 

 an artificial event, which can be repeated with ease and ra- 

 pidity, it not being essential, he thinks, that those observa- 

 tions should very closely imitate the transit of a star over 

 the wires of a telescope, inasmuch as it is the general condi- 

 tion of the nerves which it is important to keep in training 

 more than any thing peculiar to this or that kind of observa- 

 tion. Report Supt. Coast Survey, 1870, 224. 



THE EARLY EACES OF MANKIND IN IRELAND. 



Sir William Wilde made a communication before the Brit- 

 ish Association upon the early races of mankind in Ireland, 

 and ascribes the greater bulk of the Keltic population to the 

 "Firbolgs," the "Tuatha-de-Dannans," and the "Milesians." 

 The Firbolgs were described as a pastoral and agricultural 

 people, small in stature, oval-headed, straight-haired, and of 

 swarthy complexion; this associated with blue-gray eyes and 

 dark eye-lashes. These are supposed to have been the first 

 builders of the earthen forts, and to have buried their dead 

 without cremation, but erecting tumuli or cromlechs as their 

 monuments. They, with the lair-skinned Dannans, consti- 

 tute the bulk of the farm-laborers who migrate to England 

 during the harvest season. 



The Tuatha-de-Dannans are described as large-sized, fair- 

 skinned, and round-headed. They were warlike, musical, and 



