SOLAR ECLIPSE, MAY 6, 1883. 



87 



of the beat of tlie corona, and are not sensitive enough for .such refined measurement. Tiieir use 

 is to measure the efteet of heat which is received from the sun and by reflection from the atmos- 

 phere — the heat which is a factor in causing vegetable growth; they do not claim a position as 

 delicate physical instruments. The observations show tliat during the eclipse the amount of heat 

 gradually diminished until practically none was recieived, and the temperature of night was 

 attained. 



2. The maximum point of the curve in the first partial phase is at about 10.08 a. m., or four 

 minutes after the first contact. This four minutes covers whatever tardiness the instruments 

 possess, as well as the natural increase of solar heat in the morning, until it was overbalanced 

 by the direct cufctiug off of a jtortion of the sun's heat. The ininimum point of the curve is at 

 about 11.40 a. m., or tliree minutes after the ob.served time of third contact. This time is some- 

 what uncertain, as from the nature of the case this portion of the curve is drawn arbitrarily, the 

 intensities having become indeterminate. The second maximum is at 1.15 j). m., four minutes 

 after the last contac was noted. The afternoon observations do not indicate as great intensities 

 as the morning, as is further indicated by the computed diathermancy constants given below. 

 The sky was observed to be quite hazy as the day advanced. 



3. A measure of the clearness of the atmosphere can be obtained by computing the constant 

 J) in equation (4), using for A the viilue 2.322, and for / the intensities computed from the 

 observations. This computation has been made for the two observations at 10.00 and 10.05 a. 

 m. at the beginning of the eclipse, and for those at 1.15 and 1.30 p. m., after its close. The fol- 

 lowing are the results : 



The mean value of p corresponding with the adoi)ted value of A is 0.751. It is seen, theif, 

 that at the beginning of the eclipse the clearness of the'sky was about normal, or slightly below 

 the normal, but that after the- eclipse it was decidedly below the average value. The computa- 

 tion, therefore, confirms the evidence given by the intensities on May 6 compared with other 

 days, and also the ocular evidence, that during the eclipse the skj was not wholly clear, but that 

 there was a perceptible haziness. 



VN 5. BOTANY OF CAROLINE ISLAND. 



(Collections by Dr. Dixox aud identifications by Dr. William Trelease, of the University ofWi-sconsin.; 



Dr. Dixon made a complete collection of botanical specimens from the south island, and 

 included in his examination all the portions of the whole group visited by him. This collection was 

 turned over by me to Professor Trelease for examination, and I have to express the thanks of 

 the expedition to him for his very satisfactory report, which follows. 



The collection was in a very poor state for examination, and must have presented great 

 difficulties. I would call attention to the fact that out of 28 .specimens collected a great number 

 (21) are, I believe, not included in the report of the Wilkes exploring expedition. 



