^4 On a New Form of Spectroscope. 



yet. On a former occasion I stated to you 'my belief that 

 the key to our more general meteorological changes and 

 conditions of the earth's surface would eventually be found 

 in the variations of the condition of the sun, and if one may 

 be allowed to draw a bi'oad inference from the facts I have 

 brought under your notice, it would in some degree go to 

 support this belief Such rapid strides have of late years 

 been made in our knowledge of solar physics, and in the 

 means of observing every state and change of our luminary, 

 that if the relations suggested really do exist, we may 

 reasonably hope that at no very remote period they may be 

 traced out from their intricate involvement. 



Art. XX. — On a Neiv Form of Spectroscope. 

 By R. L. J. Ellery, Esq. 



[Read 12th March, 1871.] 



This was an oral description of a new form of a seven 

 prism Spectroscope which was exhibited to the meeting. 

 The instrument in its general construction did not materially 

 differ from other large spectroscopes. The new feature was 

 the method adopted for adjustment of the prisms to 

 minimum deviation, which could be accomplished by simply 

 pointing the observing telescope to any desired part of the 

 spectrum ; and it was so arranged that any number of 

 prisms,^ from one to seven, could be used and adjusted by 

 the mechanism. 



The accompanying diagram will fully explain the 

 arrangement, p^p^p^p^p^p^ p' are the prisms attached 

 to the link work jointed at ah c d e f g. The first 

 prism is pivoted to the table at the point F, and to 

 the last prism is attached a right-angled piece R A, 

 pivoted at the joint h. By moving the arm A of the right- 

 angled piece, the whole series of prisms is moved, the link 

 work expanding or contracting by the slotted radial arms, 

 moving over the centre pin C, which again travels in the slot 

 S S in the table. It will readily be seen, therefore, that all 

 the parts being properly gauged and made, the whole series 

 of prisms will be moved symmetrically by moving the arm 

 A, which is rigidly fixed to the observing telescope, and it 

 follows that by pointing the telescope to any desired part of 

 the spectrum, the prisms will all move proportionally, and 



