34 PRACTICAL HISTOLOGY. 



tion. What is wanted for ordinary microscopic work 

 undoubtedly is an instrument resembling that shown in 

 Fig. i ; it matters not who makes it, provided it be well 

 made and at moderate cost. In the Edinburgh school, 

 Hartnack's microscope has always been recommended 

 hitherto, because it has met the requirements of the student 

 better than other forms of the instrument. Quite recently, 

 however, Mr. Swift of London sent for my inspection a 

 student's microscope somewhat resembling Hartnack's. I 

 was struck by the excellence of many of its parts. The 

 objectives are % inch and i inch, the former is of low angle, 

 and the lens sent to me as a sample was certainly a better 

 lens than the majority of Hartnack's No. 7. Its power was 

 considerably higher. Swift's lens, however, wants a thin 

 brass ring round its margin to give it more protection. His 

 medium eye-piece (C), equal to Hartnack's No. 3, is excel- 

 lent, but the shallow eye-piece (D), though better than 

 Hartnack's No. 4, is of little use. With the -^--inch objective 

 and the C eye-piece it is possible by simply altering the 

 length of the telescope tube to get a power ranging from 

 250 to 450 diam., a great convenience, and in this respect 

 surpassing Hartnack. The pedestal, the hinge, the pillar, 

 and the support of the body of the microscope, are all 

 steadier than in Hartnack's III. A microscope* (Fig. i). 

 The fine and coarse adjustments are certainly better made. 

 But the instrument is not yet perfect. The diaphragm is 

 let into the stage from above, so that the disc rotates just 

 under the slide ; a faulty arrangement, with which it would 

 be impossible to keep the stage clean. Acids getting be- 

 tween the diaphragm and the stage would spoil everything. 

 The object of the arrangement is to have a rotating dia- 

 phragm with its apertures close to the slide, but until a 



* Hartnack's No. III. A microscope, with objectives 3 (i inch), 

 and 7 (not quite \ inch), and oculars 3 and 4, may be obtained from 

 Bryson, 60 Princes Street, Edinburgh, for j : los. ; also from Tisley 

 and Spiller, 172 Brompton Road, London, S.W.; and Baker, 244 

 High Holborn, London, W.C. Mr. Swift's (43 University Street, Tot- 

 tenham Court Road, London) microscope above alluded to, with 

 -in. and i-in. objectives, and C and D ocular, similar to Hartnack's, 

 costs 6 : I2s. 



