dequacy in the number and variety of data, but he is careful to shut out all possible error caused by idiosyncrasy in himself. Though not perhaps in astronomical observations such as those above implied, yet in all astronomical observations where the element of time is important, he makes allowance for the intervals occupied by his nervous actions. To fix the exact moment at which a certain change occurred, his perception of it has to be corrected for the “personal equation.” As the speed of the nervous discharge varies, according to the constitution, from thirty to ninety metres per second, and is somewhat greater in summer than in winter; and as between seeing a change and registering it with the finger, there is an interval which is thus appreciably different in different persons; the particular amount of this error in the particular observer has to be taken into account.
正文 Chapter I Our Need of it（2）（2 / 3）