102 POPULAR SCIENCE MONTHLY. 



searched. Owing to the increased cloudiness at the end of totality, the 

 search is not quite complete to the fainter magnitude, yet it seems altogether 

 probable that were there any considerable number of bodies as bright as seven 

 and three fourths magnitude, some of them would have been detected. A 

 planetary body thirty-four miles in diameter would, under the conditions con- 

 sidered, appear as a star of seven and three fourths magnitude. The total mass 

 required to produce the change observed in the orbit of Mercury is about one 

 half the mass of the planet. It would require, therefore, no less than seven 

 hundred thousand bodies thirty-four miles in diameter and as dense as Mercury 

 to equal such a disturbing mass. 



From the observations detailed above it does not seem possible that suffi- 

 cient matter exists in the region close to the sun in the form of bodies of 

 appreciable size to account for the observed perturbations. 



Belief in the existence of intramercurial planets has been based 

 upon anomalies in the orbital motion of Mercury, and Perrine's work 

 has gone far to show that the discrepancies must seek some other ex- 

 planation. Had the thicker clouds not reduced the minimum visible 

 in one third the area observed in Sumatra from the ninth to the sixth 

 magnitude, it is a question whether one could recommend that this 

 search be continued at future eclipses. However, so long as we admit 

 that it is a question, the effort to secure definite results, positive or 

 negative, should be made. It is not impossible that existing bodies 

 could have been in the region of thicker clouds, or in that occupied 

 by the moon and inner corona, or in areas outside the limits of the 

 strip six degrees wide. 



The eclipse of August 30, 1905, will occur when the earth is seven 

 degrees from the plane of the solar equator. The maximum distance 

 occurs September 7. It will therefore be advisable to search over a 

 region of considerably greater width than was the case in 1901. Inas- 

 much as increased area means increased instrumental equipment, ex- 

 pense, and difficulty, a corresponding shortening of strip to be observed 

 would perhaps be justified. It is to be hoped that observing parties 

 well equipped for the intramercurial search will be located in Labrador, 

 Spain, Tunis and Egypt. If clear weather prevails at any of the four 

 stations, very valuable results may be secured. Should a new planet 

 be observed at three such stations, the enormous interest attaching to 

 its discovery would be heightened by the fact that its approximate 

 orbit could be determined at once. If no planets are revealed on first 

 class plates, the negative result would be scarcely less valuable, though 

 certainly less interesting, than positive results; and the intramercurial 

 question would cease to be a pressing eclipse problem. 



The sun's altitude will be only 26° in Labrador and 23° in Egypt. 

 The altitude of the lower end of the area to be photographed will be 

 small at these stations. The atmospheric disturbances and absorption 

 at such low altitudes will require that the exposures be lengthened. 

 Perhaps a better plan would be for the Labrador party to cover the 



