Faieclough. — On the Constitution of Comets. 477 



to be the result of mere accident. Sometimes unimportant circumstances 

 — such as the position of the door or fireplace, or the best place for the 

 blackboard — have decided the matter. More frequently it has depended on 

 the desire to have the faces of the children in full light. Against this I 

 have already declared myself. Most frequently, however, the wish to place 

 the children as near as possible to the master has regulated the arrange- 

 ment, and has led to placing the seats in a horseshoe form ; but also in 

 this arrangement only one-third of the children can have a proper light. I 

 admit it is very difficult to answer all requirements in this respect, especially 

 if the schools have not been built with a proper consideration to the 

 hygienics of the human vision. However, in most class-rooms it would be 

 easy to make the necessary alteration — to have the light- come from the 

 left-hand side, and, by raising the benches one above the other, or, simpler 

 still, by sufficiently raising the master's place, to enable the teacher to sur- 

 vey the whole class at a glance. 



I am afraid my advice in tbis matter will not soon be practically 

 followed, as even in Europe only after years of urging and preaching have 

 the necessary alterations been made in schools ; but my paper has at least 

 drawn attention to the matter, and it must rest in the future what fruit 

 it will bear. 



Aet LX. — On the Constitution of Comets. By the Eev. P. W. Faieclough. 

 [Read before the Southland Institute, 10th October, 1882.] 

 Keplee, with the prescience of genius, supposed that comets throng in 

 space as fish in the sea. It is true that only some 650 comets are recorded 

 as seen during the Christian era, and that a considerable number of these 

 have been reappearances of periodic visitors. But of these 650, about 120 

 have been seen in the Nineteenth Century, — mostly telescopic, however. 

 This large number is owing to improved methods of observiug. As many 

 as eight have been seen in one year, and we have in our morning sky the 

 fourth for the year 1882. Now, it is certain that not half the comets that 

 approach the sun, within the range of the telescope, are seen by man. It 

 may also be regarded as highly probable that vast numbers of comets have 

 their perihelia at distances which preclude their discovery. 



A comet crossing the solar frontier with the momentum of a few miles 

 per annum, along a line forming an angle of 45° with the radius from the 

 sun's centre to the comet's centre, at the moment of crossing, would secure 

 a perihelion distance of many millions of miles. If, however, the momen- 

 tum amounted to miles per hour, the comet would be carried far too wide 

 of the sun to be observed by the inhabitants of the earth. 



