198 ASTRONOMY. 



The solar eclipse of 1878 is noteworthy, since it was visible over a large 

 l)ortion of civilized country, each part of which it was easy to reach by 

 cheap transportation. The Congress of the United States also placed 

 the sum of $8,000 at the disposition of the Naval Observatory, which 

 was expended in providing the necessary instruments and in placing 

 men and instruments in the proper field. The expenses of 27 observ- 

 ers — mostly astronomers at various universities or colleges — were paid, 

 wholly or in part, from this sum. This governmental action is note- 

 worthy in the history of the country, as indicating the means by which 

 alone government aid to science can be afforded under our form of ad- 

 ministration, and it would seem that the question of the " endowment 

 of research," which has been agitating Great Britain, has here been 

 quietly solved. The Naval Observatory accounted to the Treasury for 

 the money, and the funds were spent in placing its own parties and 

 those headed by all the eminent astronomers of the country in the held, 

 and under its auspices liberal arrangements with the customs depart- 

 ment and the railways were made for the benefit of foreigners. 



To come to the most important particulars of the volume before us: 

 It is preceded by the elaborate Instructions to Observers, com [»iled by 

 Prof. Harkness, of which it may be said that it is the most complete, 

 and on the whole the most satisfactory, which we have. Guided by 

 these instructions, the amateur observers prepared their sketches of the 

 corona and made their observations. 



In previous eclipses the princii^al point to be noted in regard to such 

 sketches has been that each sketch differed so much from every other 

 that only a knowledge of the circumstances under which tbey were 

 made could allow one to believe that they were representations of the 

 same phenomenon. Here, however, so many sketches were made, each 

 one readily comparable with the photographs made by the parties of 

 Professors Hall, Harkness, and Holden, that for the first time a 

 kind of order can be evolved from what has previously been but chaos. 

 The photographs serve always as a standard, and it is seen that each 

 sketch represents (and exaggerates) one or more special features, the 

 other features remaining unnoted. Thus, by combiuhig the whole set 

 a very fair general representation can be had. This is one most impor- 

 tant lesson. The photographs themselves are of the highest excellence. 

 The parties of Prof. Hall and of Prof. Harkness were provided with 

 complete outfits, and each secured a series of photographs of exposures 

 varying from 3 to 60 seconds. The pictures with the shortest expos- 

 ures give the details of the corona near the Sun ; those of longer ex- 

 posures giving details furtht^r out. In these latter pictures tbe inner 

 corona is much over-exposed, and its details are thus lost ; but by a 

 combination of the set the whole can be built up out to the distance 

 of 20' from the Sun's edge. 



A single photograph was taken by Prof. Holden's party, which ad- 

 mirably supplements the others, as it begins where the others leave 



