1869.] New Arrangement of Binocular Spectrum-Microscope. 443 



moon appears to indicate an elevation of temperature through 500° Fahr.* 

 In deducing this result allowance has been made for the imperfect ab- 

 sorption of the sun's rays by the lunar surface. 



In the present imperfect state of these observations it would be prema- 

 ture to discuss them at greater length ; but as some months must elapse 

 before any more complete series can be obtained, and the present results 

 are sufficient to show conclusively that the moon's heat is capable of being 

 detected t with certainty by the thermopile, I have thought it best to send 

 this account to the Royal Society ; and I shall be most happy to receive 

 suggestions as to improvements in the method of working, and as to the 

 direction in which it may be most desirable to carry on future experiments. 



IV. " On a New Arrangement of Binocular Spectrum-Microscope. " 

 By William Crookes, F.R.S. &c. Received April 23, 1869. 



The spectrum-microscope, as usually made, possesses several disadvan- 

 tages : it is only adapted for one eyef ; the prisms having to be introduced 

 over the eyepiece renders it necessary to remove the eye from the instru- 

 ment, and alter the adjustment, before passing from the ordinary view of an 

 object to that of its spectrum, and vice versd ; the field of view is limited, 

 and the dispersion comparatively small. 



I have devised, and for some time past have been working with, an in- 

 strument in which the above objections are obviated, although at the same 

 time certain minor advantages possessed by the ordinary instrument, such 

 as convenience of examining the light reflected from an object, and com- 

 paring its spectrum with a standard spectrum, are not so readily associated 

 with the present form of arrangement. 



The new spectrum-apparatus consists of two parts, which are readily 

 attached to an ordinary single or binocular microscope ; and when attached 

 they can be thrown in or out of adjustment by a touch of the finger, and 

 may readily be used in conjunction with the polariscope or dichrooscope ; 

 object-glasses of high or low power can be used, although the appearances 

 are more striking with a power of ^-inch focus or longer ; and an object as 

 small as a single corpuscle of blood can be examined andits spectrum observed. 



* This may seem a very large rise of temperature ; but it is quite in accordance with 

 the views of Sir John Herschel on the subject (Outlines of Astronomy, section 432 and 

 preceding sections), where he says that, in consequence of the long period of rotation of the 

 moon on its axis, and still more the absence of an atmosphere, " The climate of the moon 

 must be most extraordinary, the alternation being that of unmitigated and burning sun- 

 shine, fiercer than that of an equatoreal noon ; and the keenest severity of frost, far ex- 

 ceeding that of our polar winters, for an equal time." And again, " . . . . the surface of 

 the full moon exposed to us must necessarily be very much heated, possibly to a degree 

 much exceeding that of boiling water." 



t Mr. Sorby in several of his papers (Proc Roy. Soc. 1867, xv. p. 433 ; 1 How to Work 

 with the Microscope,' by L. Beale, F.R.S. , 4th edition, p. 219) refers to a binocular 

 spectrum-microscope ; but he gives no description of it, and in one part says that it is not 

 suited for the examination of any substance less than of an inch in diameter. 



