242 Mr. W. Huggins on a Hand Spectrum-Telescope. [Jan. 23, 



briglit lines, one of them broad, crossed by a faint continuous spectrum. 

 The magnifying-power of the telescope is insufficient to show the three di- 

 stinct lines of which the spectrum of the nebula consists. The conti- 

 nuous spectrum is due to the stars of the trapezium, and the other 

 fainter stars scattered over the nebula. 



For the purpose of testing the efficiency of this instrument as a meteor- 

 spectroscope, I observed the spectra of fireworks seen from a distance of about 

 three miles. The bright lines of the metals contained in the fireworks 

 were seen with great distinctness. I was able to recognize sodium, mag- 

 nesium, strontium, copper, and some other metals. 



Unfortunately I was prevented from making the use of the instrument 

 which I had intended at the display of meteors in November 1866. 

 I have, however, great confidence in the suitability of the apparatus for 

 the prismatic observation of meteors and their trains. 



As the instrument is not provided with a slit, it is applicable only to 

 bright objects of small size, or to objects so distant as to subtend but a 

 very small angle. It is obvious that if the object has a diameter smaller 

 in one direction than in any other, as would usually be the case with the 

 trains of meteors, the instrument should be rotated to take advantage of 

 the form of the object. The most favourable position will be when the 

 smallest diameter of the object is perpendicular to the height of the 

 prisms. In this way I have seen the lines of Fraunhofer in the spectrum 

 of the moon when a very narrow crescent. 



In the case of objects which appear as points, a small breadth may be 

 given to the spectrum by a cylindrical lens fitted in a little cap which slips 

 over the eye-lens, and is placed next to the eye. 



As some of the advantages which this instrument possesses over an or- 

 dinary spectroscope, or over a prism held before the eye, may be stated 

 the comparatively large amount of light which the object-glass collects, 

 the great facility for instantly pointing the instrument to the object de- 

 sired, which the large field of view affords, and in some cases the magni- 

 fying-power of the instrument. 



It may perhaps be mentioned that secret signals might be conveyed 

 at night by means of the temporary introduction of certain suitable sub- 

 stances, as preparations of lithium, copper, strontium, &c., into the flame 

 of a lamp giving a continuous spectrum ; the presence of the bright lines 

 due to these substances would not be perceived except by an observer 

 provided with a spectrum-telescope, to whom they might convey infor- 

 mation in accordance with a previous arrangement. 



This little instrument, held in the hand and directed to the place of the 

 sun during its eclipse in 1868, might enable an observer, who was not 

 provided with larger apparatus, to give an answer to the important ques- 

 tion whether the bright prominences are self-luminous or reflect solar 

 light. At least it would be possible for him to determine the general 

 character of the spectrum of a bright prominence so far as to learn whether 



