162 Miscellaneous Intelligence. , 



that the ether, or resisting medium, is diffused through all space ; 

 that its density diminishes in the inverse ratio of the square of the 

 sun's distance, and that the resisting force is always proportional 

 to the square of the actual linear velocity of the comet. — Bib. 

 Univ. xli. 3. 



3. New Method of measuring the Power of Telescopes, by M. 

 Valz. — The method consists in measuring the angle which the 

 rays, from a body of known diameter, form when they leave the 

 telescope. The sun, by reason of its brightness, appears the object 

 best fitted for this purpose. Its image, therefore, formed at a given 

 distance from the eye-glass, is to be measured, and divided by this 

 distance, and by the double tangent of the semi-diameter of the 

 sun. By making the distance equal to the cotangent of the sun's 

 diameter, the number in parts of the scale employed, included in 

 the extent of the image, will express the quantity of enlargement. 

 Thus, in January, the image should be received and measured at 

 105 parts from the eye-end of the telescope ; in July, at 109 parts ; 

 in April and October, at 107 ; but rigorously this quantity must 

 be diminished by the diameter of the small image, which is formed 

 at the point from whence the distance is measured. When the field 

 of the telescope is smaller than the sun's diameter, we may pre- 

 viously trace a circle upon a screen which is then to be made to 

 coincide with a part only of the edge of the sun. But it may be 

 found preferable in such cases to employ the known diameter of 

 the field of view in place of that of the sun ; and if it has not been 

 previously ascertained, it may be determined at the same operation 

 by the time which a solar spot takes to traverse centrally the image 

 received on the screen. — Bib. Univ. xli. 25. 



4. Brown's Active Molecules. — Mr. Holland, the inventor of a 

 microscope sold by Carey, of the Strand, has inclosed some of 

 the particles described by Mr. Brown, as active molecules, be- 

 tween glass and talc, closing the whole hermetically so as to ex- 

 clude, as much as care could do, all interference of external causes. 

 Notwithstanding this, the motion continued equally vivid, even 

 after ten days. The lens used had a focus of the thirtieth of an 

 inch ; and the particles were obtained, as we understand, from 

 gamboge. 



5. Force of Running Water. — A few facts and observations on 

 the power of running water have been communicated to the 

 Geological Society by Mr. Culley, one of its fellows. The heavy 

 rains which fell during three days of August, 1827, swelled to an 

 unusual height the small rivulet called the College, which flows at 

 a moderate declivity from the eastern water-shed of the Cheviot 

 Hills, and caused that stream not only to transport enormous 

 accumulations of several thousand tons weight of gravel and sand 



