706 EECOED OF CURKENT RESEARCHES RELATING TO 



the objectives and compound body should be abolished, a new and 

 more expeditious method has been adopted. Instead of screwing the 

 body on to the arm, and then screwing the objective into the body, 

 the objectives are made to slide down smoothly into the arm (as 

 illustrated in the iigure), and may thus be used as simple powers, for 

 dissection. When the compound body is required, it may be in- 

 stantaneously slid over the objective, and is thus ready for use, with 

 a great saving of time and trouble. 



Should it be desirable at any time to use objectives having the 

 Society screw, provision is made for so doing, by the lower end of the 

 tube which passes through the arm being cut with such a screw. A 

 loose adapter having the standard screw is also supj^lied with each 

 instrument, which will receive the objectives belonging to it ; by 

 screwing them into the adapter they may be used with another 

 Microscope if necessary. 



The following is the (verbal) description which Professor Huxley 

 gave of the instrument :* — 



" In a Microscope to be used for delicate dissections, certain quali- 

 fications were absolutely essential. In the first place, there must be 

 perfect steadiness, the stand must be firmly and well supported, and 

 be of sufiicient strength and weight to bear the pressure put upon it 

 without moving. Next, it must be of convenient height, so that in 

 working the hands may get a steady suj)port ; it should fulfil these 

 two conditions, and yet not be so large as to be clumsy. The next 

 point was as to the lenses : they should be of such a form as to give a 

 maximum of power, and yet at the same time afford sufficient distance 

 between them and the object to admit of needles being moved freely 

 to an angle of 60'' with the surface of the plate, because the efficiency 

 of the needles obviously depended upon the angle at which they could 

 be used, and if a lens were made with a wide face it would very often 

 interfere with the movements of the needles. Then there was another 

 point of still greater importance : when a careful dissection had been 

 made, it often became desirable to examine it with a much higher power 

 than the one which had served the purpose of preparation, and provision 

 ought to be made to enable as high a power as was desired to be 

 brought to bear without disturbing the object, and this could only be 

 done by placing a compound body above the simple lens. 



[The President then exhibited the instrument which he had devised 

 to meet these requirements as described above.] 



" In offering the instrument for discussion, the question would arise 

 as to the best form of lens to be employed, and he hoped to receive the 

 opinions of the members upon this and other matters ; but at present he 

 used an ordinary low-power achromatic objective, made so as to slip into 

 the arm without screwing; there was great convenience in thus mounting 

 and using a simple lens. . . . Now, supposing they had made their dis- 

 section successfully, the point was how to be able to convert the instru- 

 ment at once into a compound Microscope without disturbing either the 

 lens or the object. One of his aims in life had been to get Microscope- 

 makers to abolish screws, which he regarded altogether as abominable 

 * ' Jomu. Quek. Micr. Club,' v. (1879) p. 144. 



