10 Mr. H. Meikle on the Existence of 



a function must possess ; but it is impossible that one can be 

 found that will accurately represent a probability, of which 

 we never can acquire a perfect knowledge. Therefore, al- 

 though the same conclusion be still brought out, yet, as the 

 reasoning involves precarious suppositions, the fundamental 

 principles will not be placed in a light so simple and clear 

 and stead}' as when nothing extraneous is introduced in the 

 demonstration. It has been proved in the case of a great 

 number of observations, that the principle of the least squares 

 will hold good, whatever law of probability be adopted ; and 

 hence we may derive an argument that such laws are foreign 

 to the demonstration, since thej' disappear at the conclusion. 

 If we admit that, whatever be the expression of the chance of 

 an error, the mean of the squares of the errors will converge 

 to a fixed limit as the observations inci'ease in number, the 

 second of the two demonstrations given above will be con- 

 clusive in all possible laws of probability. 



But, allowing that the method of the least squares is fully 

 established, it is not sufficient for the purposes of astronomy 

 in its present state of improvement. An element, although 

 computed in the best way, can only have a degree of accuracy 

 relative to the precision of the observations. It thus becomes 

 necessary to estimate the uncertamty in the result obtained, or 

 to assign the probability that the remaining error amounts to 

 a tenth, or some given part, of the whole. But the discussion 

 of the subject in this new view of it would exceed our pre- 

 sent limits, and must be left to a future occasion. 



.lanuarv 8, 182r>. Jamks IvorY. 



II. Hints tending to disprove the Existence of distinct Calorific 

 Rays in the Sunbemn. By Mr. Henry Meikle. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 

 T^HAT great mechanical genius Dr. Hooke seems to have 

 -■■ been the first who suspected that the sunbeam contains 

 Tays which illuminate without producing heat. In this opi- 

 nion he has been followed successively by M. Scheeie, Sir 

 William Herschel, and Sir Henry Englefield, who are well 

 known as able experimenters. Among other conclusions, the 

 two last thought they had established that the sun emits se- 

 veral distinct sorts of rays, especially illuminating rays, as 

 already mentioned, which give no heat; and on the other hand 

 calorific rays which are not accompanied with light. For on 

 placing a thermometer in the well-known figure called the 



spectrum. 



