174 REPORTS OF inve;stigations and proje;cts. 



separated regions of the globe during the past 60 years, investigated by 

 rigorous methods of statistical correlation. One conclusion is that there is 

 a fluctuation in the general temperature of the globe having the same period 

 as that of the sun's spots, and a coefficient of about o.i4°C. The entire 

 range during the 11 -year period is therefore about 0.28° C, or about 0.5° F. 

 Apart from this, there are no perceptible fluctuations, and any imperceptible 

 fluctuations which may exist can not exceed a fraction of i per cent of the 

 whole, so that their influence on terrestrial temperatures and other meteoro- 

 logical elements is too small to produce any important efifect. It should be 

 added that the conclusions relate only to the thermal radiation, and not to 

 magnetic or electric emanations. 



Nezv Theory and Tables of Mars. — It has been found that Professor New- 

 comb's tables of Mars, published ten years ago by the Nautical Almanac 

 Ofifice, fall below the degree of precision required in astronomy, and must be 

 reconstructed. The most difficult part of the work will be the recomputation 

 of the general perturbations of the second order, which can be done only by 

 an experienced mathematician, well trained in this kind of work. What has 

 so far been done comprises the computation of an ephemeris of the planet 

 since 1753, when accurate observations commenced. This ephemeris is still 

 unfinished and is laid aside to complete the work on occultations. 



Astrophysics. — The great interest attaching to the so-called canals of Mars 

 led the writer to make an experimental study of certain branches of the 

 psychology of vision, relating especially to the appearance presented by faint 

 and difficult markings on the surface of a planet. The results of this study, 

 with their application to the case of Mars, were published in the Astro- 

 physical Journal for July, 1907. 



Methods of Probable Inference, Especially in Statistics. — During a visit 

 to California last summer Professor Newcomb took occasion to put the pre- 

 liminary chapters of a work on this subject into shape, and to develop some 

 formulae of demography. This is the work with which he expects to be 

 mainly occupied when that on occultations is out of the way. 



Russell, Henry N., Princeton, N. J. Grant No. 207. Photographic determi- 

 nation of stellar parallaxes. (For previous reports see Year Book No. 

 3, pp. 92, 93, and Year Book No. 5, p. 89.) $1,000. 



The work of the past year has consisted in the measurement and reduction 

 of photographs taken at Cambridge, England, by Dr. Russell and Mr. A. R. 

 Hinks. During the year 97 plates have been measured, making a total of 

 219 plates, of 38 fields, which have been measured and completely reduced; 

 28 additional plates, which were very kindly obtained by Mr. Hinks after Dr. 

 Russell left Cambridge, have just been received and will be measured. 



