270 



like circles, parabolas, &c., are similar curves ; tables constructed for 

 one value of the parameter apply to all by simple proportion. 



He then enters into an analytical investigation of the equations 

 suited for bis purpose, and finally concludes his paper with four 

 tables. The first consists of six columns, and contains correspond- 

 ing values of the parameter ; the exponential function or inverse 

 logarithm of the span, divided by the parameter ; the versed sine, the 

 length, the tension at the point of support, and the angle of suspen- 

 sion ; all computed for a semi-span of 100 parts, for the ordinary 

 catenary, and for a parameter varying from 1000 to 2000. 



Table 2. contains the same quantities for a constant parameter 100, 

 and for all values of the semi-span from 1 to 100. 



Table 3. is adapted to the catenary of equal strength, and corre- 

 sponds to Table 1 . in the ordinary catenary ; the constant span being 

 100, and the parameter varying from 70 to 1000, with an additional 

 column expressing the weight of the whole curve ; while Table 4. 

 exhibits the same things for this curve, arranged in the order of 

 Table 2. 



By the aid of these Tables all the requisite particulars may easily 

 be found in any case proposed in practice. 



On Magnetic Influence in the Solar Rays. By Samuel Hunter 

 Christie, Esq. M.A. F.R.S. of Trinity College, Cambridge ; Fellow 

 of the Cambridge Philosophical Society : of the Royal Military 

 Academy. Communicated November 15, 1825. Read January 19, 

 1826. [Phil. Trans. 1826, Part III. p. 219.] 



The object of this communication is to show, by a series of expe- 

 riments, that the sun's rays possess sensible magnetic properties, 

 which are observable in the vibrations of a magnetic needle exposed 

 to them independent of their heating effect ; and also to point out 

 the changes which take place in the intensity of a needle's mag- 

 netism, from changes of temperature, as deduced from its times of 

 vibration. 



The main fact noticed by the author, indicative of a magnetic in- 

 fluence in the solar rays, is this ; that a magnetic needle vibrating, 

 exposed to the rays of the sun, comes to rest more quickly than 

 when vibrating in the shade. 



A needle, six inches long, contained in a brass compass-box with 

 a glass cover, was suspended by a fine hair, and made to vibrate, 

 alternately shaded and exposed to the sun. The shade was pro- 

 duced by a wooden screen, supported four feet above the box. It 

 was then found that (setting off from the same point,) the 100th 

 vibration could be very distinctly noted in the shade, but none 

 further than the 75th in the sun. So far, too, from the increase of 

 temperature in the needle having caused the vibrations to be per- 

 formed slower in the latter case, they were actually executed some- 

 what more rapidly. 



