January 16, 1903.J 



SCIENCE. 



105 



Saint Loup's Linkage: Professor L. G. 



Weld, University of Iowa. 



The linkage described by M. Saint Loup 

 in the Comptes Bendus for 1874 was dis- 

 cussed with reference to its application to 

 the solution of cubic equations. An in- 

 strument constructed upon the principle 

 in question was exhibited and operated. 

 The failure of the device to give the rni- 

 merically greatest root, or the single real 

 root, was pointed out and explained. At- 

 tention was also directed to the fact that 

 this root corresponds to a conjugate point 

 of the locus traced by the linkage and can 

 not, therefore, be reached by continuous 

 motion in the plane of reals. 



A Device to Prevent Personal Equation 

 in Transit Observations: Professor S. 

 P. Langley, Secretary of the Smith- 

 sonian Institution. 

 Read by title. 



The Solar Constant and Related Problems: 

 S. P. Langley, Secretary of the Smith- 

 sonian Institution. 



Our absolute dependence on the light 

 and warmth received from the sun makes 

 the study of solar radiations of the highest 

 utilitarian value, even apart from their 

 scientific interest. So little is even now 

 certainly known about the actual amount 

 of the solar radiation, and the absorption 

 of it which the solar gaseous envelope and 

 the earth's atmosphere together cause, 

 that it is doubtful if any one can predict 

 just what influence a given change in the 

 total radiation of the sun would produce 

 on earthly warmth and life. 



Early work of the author at Allegheny 

 and upon Mt. Wliitney relating to these 

 studies was referred to, however, as show- 

 ing certain limits within which important 

 predictions could be made, and then atten- 

 tion was drawn to the present investiga- 

 tions of the Smithsonian Astrophysieal 

 Observatory. The great improvements in 



instriunental equipment within recent 

 years were pointed out. Charts were ex- 

 hibited illustrating how the total radiation 

 expressed in terms of each wave-length as 

 it reaches the eai'th was accurately repre- 

 sented, by means of an observation lasting 

 only a few minutes, where formerly over 

 two years' labor were required to do still 

 less. Other charts showed how these 

 amounts were corrected, step by step, until 

 the rate of the sun's radiation on the out- 

 side of the earth's atmosphere (commonly 

 known as the solar constant) is determined. 



The absorbing action of water vapor in 

 the air was shown by a chart of results 

 extending from March to November. It 

 was stated that a yearly cycle of these ab- 

 sorption effects is recognized. 



Attention was especially called to the 

 probably great utilitarian importance of 

 variations of absorption in the solar en- 

 velope, in their effect upon all life, and to 

 the consequent utility as well as scientific 

 interest of the work now being renewed 

 here to determine this with hitherto un- 

 known fullness. 



Good Seeing: S. P. Langley, Secretary of 



the Smithsonian Institution. 



Astronomers have at all times been hin- 

 dered in all delicate observing by the dis- 

 turbances arising in our own atmosphere, 

 even in clear weather. The ill effect of 

 these disturbances on the telescopic image 

 is known commonly as 'boiling' (as con- 

 trasted with 'good seeing'), and it is the 

 great enemy to accurate observation. 

 Within recent years, therefore, there has 

 been a movement to establish observatories 

 in the most favorable localities to avoid 

 this difficulty, regardless of all considera- 

 tions of convenience. The aiithor who has 

 made a special study of the subject on 

 mountain tops and elsewhere, has been led 

 to think that the major part of the dis- 

 turbance arises in the air comparatively 



