On the Blood Corpuscles of the Mammiferous Animals. 195 



four long upright hooks, in which the lower end of the chimney 

 rests; or still better if the lamp be so originally constructed 



as to sustain the chimney at the required elevation without 

 such addition, by thin laminee of brass or iron, having their 

 planes directed to the axis of the wick. 



The proper elevation is best determined by trial ; and as 

 the limits within which it is confined are very narrow, it would 

 be best secured by a screw motion applied to the socket on 

 which the laminae above mentioned are fixed, by which they 

 and the chimney may be elevated or depressed at pleasure, 

 without at the same time raising or lowering the wick. Ap- 

 proximately it may be done in an instant, and the experiment is 

 not a little striking and instructive. Take a common Argand 

 lamp, and alternately raise and depress the chimney vertically 

 from the level where it usually rests, to about as far above 

 the wick, with a moderately quick but steady motion. It 

 will be immediately perceived that a vast difference in the 

 amount of light subsists in the different positions of the 

 chimney, but that a very marked and sudden maximum oc- 

 curs at or near the elevation designated in the commence- 

 ment of this letter : so marked indeed as almost to have the 

 effect of a flash if the motion be quick, or a sudden blaze 

 as if the wick-screw had been raised a turn. The flame con- 

 tracts somewhat in diameter, lengthens, ceases to give off 

 smoke, and attains a dazzling intensity. 



With this great increase of light there is certainly not a 

 correspondingly increased consumption of oil. At least the 

 servant who trims my lamp reports that a lamp so fitted con- 

 sumes very little if any more oil than one exactly similar on 

 the common plan. 



I have the honour to be. Sir, 



Your obedient servant, 



Slough, Feb. 15, 1840. J. F. W. Herschel. 



XXXVI. Observations on the Blood Corpuscles, or Red Par- 

 ticles, of the Mammiferous Animals. By George Gulliver, 

 F.R.S., F.Z.S., Assistcmt Surgeon to the Royal Regiment of 

 Horse Guards. No. III.* 

 A N account is now to be given of the blood corpuscles of 

 ''-^ several other mammalia which I have examined since 

 the publication of my last papers; and similar communica- 

 tions will be continued occasionally, until the observations 

 have been made as complete as possible, when, as already in- 

 timated, they will be presented in a systematic form, so as to 



* Communicated bv the Author, 

 0'2 



