INTENSITY OF CORONAL LIGHT DURING THE SOLAR ECLIPSE OF 1886. 373 
meter, &c., are left in position on Saturday evening.) Ascertain that your photo¬ 
meter is in the proper azimuth ; test by the Abney level that its inclination is about 
19°. Fasten the front rod securely down, so that on running the lantern backwards 
and forwards it works smoothly and without shaking the bar unduly. 
3. See that the connections to the glow lamp are properly made ; next see that the 
galvanometer is levelled and in adjustment. 
4. Give instructions that a battery of 7 cells should be in readiness for you not later 
than 6.30. Only 6 cells are to be connected up, the seventh to be in reserve in case 
of accident. 
5. At 6.30 connect up all leads, see that your lamp works properly, and take a 
reading of your galvanometer. Go round to the back of your tent and see that you 
have actually 6 cells connected up. 
6. At 7.0 request Mr. Jackson to take up bis station at the end of your table, and 
get ready to record. Go round to the galvanometer again and carefully note the 
reading of the needle, which Mr. Jackson is to record. At 7.5 take up your position 
at the photometer bar. 
7. As the light wanes follow up with the lantern, so as to get it into position with 
the least possible delay after the moment totodity begins. 
8. The preliminary drill has shown that 12 sets of double readings may be taken 
during the duration of totality. Do not, however, aim at doing more than 7 or 8 sets 
(in all 14 or 16 readings). A few readings carefully and deliberately done are 
worth far more than a large number taken very hurriedly. 
9. When you have taken your last reading let the lantern remain as you placed it 
for the reading, in order that after the eclipse its position may be verified. Be careful 
to note on which side the middle point of the photometer bar the readings are taken. 
10. There will probably be sufficient light during totality to see readily the 
numbers on the photometer bar; but, in case you have difficulty, it will be advisaole 
to have a lighted lantern in readiness under your table. 
11. At the end of totality, and therefore at the conclusion of your readings, again 
note the position of the galvanometer needle and record the deflection. 
12. Be careful not to fatigue your eye by looking too much at the Sun during the 
first stage of the eclipse. All talking to cease at 7.0. 
Observations on the Day of the Eclipse. 
The general character of the weather, as noted during the ten days prior to the 
date of the eclipse, rendered it very doubtfid whether any photometric observations 
would be at all possible a.t the time of totality. 
The following Table will serve to indicate the condition of the sky at about the hour 
of the eclipse on successive days from August 17th to the 28th. 
The amount of cloud is given on the scale from 0 to 10. 
