ASTRONOMICAL I'llKNoMKN A AN'D PROGRESS. 



39 



u iv ut tlio baso of the chromosphere to be 

 0,180iam. (ul)out seven inches of the mercurial 

 l)':in.!ii. !. TI, h,- finds the pressure at the lovel 

 of tin- niirki <>f the spots to bo about 184,000 

 atmospheres, and the pressure in the inn. r 

 .11 before named to bo not less than 4,- 

 0711, into atmospheres. 



Xmi-n/Hit* and Magnetic Storms. A }iiv:it 

 ma-notic disturbance was recorded at K.-\v 

 \ utory, January 3d, which lasted for six- 

 ; ,11 or seventeen hours, and during its con- 

 tinuance an aurora was visible. A smaller 

 disturbance began January 8th, also accom- 

 panied by an aurora. During the early part 

 of the month the extent of spots on the sun 

 was lar^orthan usual, as indicated by the pho- 

 tographic registration, as follows: 



January 1 

 6, 

 10. 

 11 

 19, 

 13 

 It 

 24 



6 groups, 2 of thorn rather largo. 



2 rather large. 



2 largo. 



1 liir^o. 



1 very large, another large. 



1 large. 



1 large. 



1 very large, another largo. 



1 large. 



Fvbruary 1st a very considerable magnetic 

 disturbance was remarked, lasting about nine 

 hours. An aurora occurred at the same time, 

 and telegraphic wires were affected by earth- 

 currents. February llth another storm took 

 place, continuing with more or less intensity 

 tor thirty hours, and an aurora appeared again. 

 The following is the record of. sun-spots for 

 February : 



February 5 . . 4 small groups, 2 larse ones. 



6 . . 5 c 1 rather large, 1 very largo. 



8.. 5 ' 2 large, 1 very large. 



I 



4 

 r> 

 7 

 I 

 B 

 4 

 3 

 28. .4 



.rge, 1 very large. 



4 large, 1 very largo. 



2 very large. 



1 large, 2 very large. 



1 large. 



1 large. 



Terrestrial Temperature and Solar Spots. 

 Mr. Cleveland Abbe, director of the Cincin- 

 nati Observatory, contributes to the American 

 Journal of Science for November an interest- 

 iii.: paper on the connection between sun-spots 

 ami terrestrial temperature. His conclusions 

 are founded on an extended comparison of 

 Wolfs tabular view of the relative frequency 

 of solar spots during the past three centuries, 

 with such meteorological tables as were ac- 

 cessible to the author. He also studied the 

 series of observations made on the Hohenpeis- 

 senberg, extending from 1792 to 1850, with but 

 five years omitted at intervals. Mr. Abbe finds 

 that the comparisons indicate a decrease in 

 the amount of heat received from the sun dur- 

 ing the prevalence of spots a result in har- 

 mony with the recent investigations into the 

 nature of the solar photosphere. The mean 

 of several years' observations, taken at the pe- 

 riod of maximum and minimum frequency, 

 makes this fact more strikingly apparent. Mr. 

 Abbe adds : " It would be interesting to seek 



tor evidence of other temperature periods than 

 tii.it dependent on the r!> \.-ii-year-pot period. 

 Tin iv uiv, iinK-i-d, plain indications of such a 

 period ut' about titty or fifty-five years' dura- 

 tion probably identical with Wolf u fifty-six 

 year period but our series of observations is 

 not extended enough to justify any exact con- 

 clusion. If we acknowledge the probability 

 of a connection between planetary configura- 

 tions and solar spots, then wo are at once led 

 to make a direct connection between the for- 

 mer and the temperature variations. Such an 

 investigation I have begun, and the indications 

 are that positive results will bo attained, and 

 such as will demonstrate that the solar spots 

 are but an imperfect index to the periodic 

 changes in the solar radiation ; these periodic 

 changes being apparently more intimately and 

 directly connected with the tides in the cool 

 atmosphere surrounding the solar photosphere. 

 The results of this investigation will be made 

 known so soon as the recent observations on 

 the Hohenpeissenberg can be incorporated into 

 the work." 



Relations between the Sun's Altitude and the 

 Chemical Intensity of Total Daylight. Messrs. 

 Henry E. Roscoe and T. E. Thorpe laid before 

 the British Royal Society in March the result 

 of a Idng series of determinations of the chem- 

 ical intensity of total daylight in a cloudless 

 sky, made by them on the flat table-land 

 southeast of Lisbon, Portugal, with the object 

 of ascertaining the relation between the solar 

 altitude and the chemical intensity. The 

 method of measurement adopted was founded 

 upon the exact estimation of the tint which 

 standard sensitive-paper assumes when exposed 

 for a given time to the action of daylight. The 

 experiments were made as follows : 



"1. The chemical action of total daylight 

 was observed in the ordinary manner. 2. The 

 chemical action of the diffused daylight was 

 then observed by throwing on to the exposed 

 paper the shadow of a small blackened brass 

 ball, placed at such a distance that its apparent 

 diameter, seen from the position of the paper, 

 was slightly larger than that of the sun's disk. 

 3. Observation No. 1 was repeated. 4. Obser- 

 vation No. 2 was repeated. 



" The means of observations 1 and 3 and of 

 2 and 4 were then taken. The sun's altitude 

 was determined by a sextant and artificial 

 horizon, immediately before and immediately 

 after the observations of chemical intensity, 

 the altitude at the time of observation being 

 ascertained by interpolation. 



u It was first shown that an accidental va- 

 riation in the position of the brass ball within 

 limits of distance from the paper, varying from 

 140 millimetres to 230 millimetres, was with- 

 out any appreciable effect on the results. One 

 of the 134 sets of observations was made as 

 nearly as possible every hour, and they thus 

 naturally fall into seven groups, viz. : 



"(1) Six hours from noon, (2) five hours 

 from noon, (3) four hours from noon, (4) three 



