224 Mapping! ivith the Micro-spectroscope, &e. 



thoughts hitherward for a short time, and learn that nature knows 

 no waste ; each particle of which the universe is composed is every- 

 where and at all times performing a duty and serving a purpose, 

 and though it may change its shape from the beautiful rosebud or 

 the gaudy butterfly to the destructive mildew or the more homely 

 grub or caterpillar, yet here when viewed through the microscopic 

 lens every part is fuU of beauty and perfectly fitted for its destina- 

 tion, either as a carrier of hfe or a destroyer of the dead — Genesis 

 and Exodus— I say again, both equally honoured by the ]Maker, 

 equally perfect, equally beautiful. 



VII. — Mapping with the Micro-spectroscope, with the Bright-line 

 Micrometer. By H. G. Bridge. 



Plate CIV. 



Now that spectrum analysis receives so much attention, as the 

 means of furnishing information in solar chemistry, and also in 

 researches in the spectral lines afforded by the combustion of metals 

 by the electric spark, and the absorption bands given by fluids, &c., 

 the bright-hne micrometer so ingeniously contrived by Mr. John 

 Browning has greatly added to the efficiency of the micro-spectro- 

 scope. 



The devising a rehable means of determining the relative posi- 

 tions of lines and bands given in the spectrum in a direct rigid 

 spectroscope was a problem of no httle difficulty, but Mr. Browning 

 has solved it ; and while it may be admitted that the use of this 

 micrometer, in order to obtain reliable results, requires some care, 

 as fi'om the nature of the whole instrument it is necessarily 

 dehcate, yet mapping by its aid is perfectly practicable, and if 

 attention be given to a few directions which I pui-pose adding for 

 the guidance of surgeons and others engaged in studying spectral 

 analysis, anyone can furnish himself with maps of the spectra of 

 his instrument, mapping many of the Fraunhofer hues, and the 

 absorption bands of tinctures, solutions, &c., for reference and com- 

 parison. In short, to show how far the use of the micrometer is 

 practicable, it is perfectly feasible to construct a map of lines whose 

 positions shall be correct to the unit of the micrometer circle. The 

 accompanying map is correct for any instrument to this degree — of 

 course this applies only to the lines and such of the absorption 

 bands as are well defined, the rest are as correct as the, in some 

 cases, somewhat nebulous nature of the bands admit of. 



It is necessary, when the instructions given in Mr. Browning's 

 pamplilet on the instrument have been attended to, to focus on the 

 object under ^examination, and that the slit be also focussed by the 



