to increasing illumination was more prompt than to decreasing. That is; They "Opened up" more quickly as the sun came out than they "closed up" as it went behind a cloud. Also the extent to which the wing coverts were separated varied with the illumination. The stronger the illumination, the wider the opening. Thus: (These figures are necessarily inexact) at about 20 or 30 foot-candles from Terry's back, there would be indications of his "splitting down the back". As it increased to say 50 he would open wider. If it increased to about 90 or 100 he would open up as wide as he ever does. As it faded, so did he close accordingly, but with somewhat greater time-lag. When the sun went completely behind the cloud and no shadows were cast he closed completely, but not until the illumination was less than that at which he opened, say 10 or 15 or thereabouts. The birds are very accurate in their orientation toward the sun at relatively low illuminations, less so at higher. That is: At say 50 foot-candles, their back are squarely placed to the incident rays. To insure that this shall be so, they frequently make almost micrometric adjustments if they have not placed them- selves accurately on first trial. At illuminations of say 100 they are not so particular, and at still higher they may even shift somewhat to decrease the radiation received per unit of area. However, the time element enters here, and the sense of satisfac- tion of the bird. Also, presumably, the air temperature. Natur- ally, if the bird has warmed his back to his satisfaction, he is not going to keep himself split down the back, sun or no sun. And if the surrounding air temperature is such as to meet with his ideas of comfort and no need for radiant heat is felt, he will not open up. All of the foregoing is, of course, in a quantitative sense, not to be assigned a high degree of accuracy. The figures given seem low, but it must be remembered that the photo-electric cell is measuring light coming from the bird's back and not that which is falling upon it. The bird's back, in- ssofar as absorption of radiation is concerned, probably approx- imates the physicists so-called black-body. It is also a good radiator of heat, but a poor radiator of light. The cell measures intensity of light, not heat. During this crude experiment the light coming from a white cloud about 90 degrees from the sun (the sun being obscured at the time) was about 900 foot candles. As a guess, a smooth surface of magnesium carbonate placed beside Terry when the sun was out fully would have given an indication of the same order. The air temperature, though not taken, was probably about 60. At no time were light and, or, temperature conditions suf- ficiently intense to induce the birds to use the spread-eagle posture, nor, for that matter, is it believed that there is an ab- olutely sharp line of demarcation between the sets of conditions determining which posture shall be used. 2 February 20th to 25th, incl. During this period there was rain every day except the 25th , ending a stretch of 17 (?) days on each of which rain fell, popular- ly considered a record. Although it is not, there are few instan- ces since official records have been kept, where it has been equal- ed. This condition of affairs has not made nesting of the thrash- ers progress very rapidly and although little work on the nest has