256 THE NORTHERN MICROSCOPIST. 
sure he would not deceive him.” ‘“ Well,” said Mr. Wurkhardt, 
“bring your objective round some evening and we will put it over 
Abbe’s Apertometer, and if it angles well I will try what I can do 
on Rhomboides.” 
After a lapse of time Mr. Wydangle took the objective to his 
friend Mr. Wurkhardt ; it was measured over Abbe’s Apertometer, 
and when the collar adjustment was properly fixed the aperture was 
found to be 0.8 or 106° air angle. Mr. Wydangle was crestfallen ; 
he exclaimed—“ what a fraud!! why I gave £8 ros. for that glass 
and I could have purchased one from Dancer of r1o® for fifty 
shillings,” when suddenly fancying he saw his way out of the 
difficulty, his face beamed with delight and he said :—“ Stay a bit, 
it has an immersion front, perhaps that is 140°.” This was tried 
over the apertometer and found to possess an aperture of 0.76, 70° 
water angle or equal to 99° air angle. It would have been a waste 
of time to have attempted the resolution of JV. rhomboides with an 
objective of this angle. It will be seen from the table on next 
page that this nominal one-eighth was more nearly a one-tenth 
with as low an air angle of 106°, and therefore the price paid for 
it does not in any way indicate its value. 
We hope we have said enough to justify the opening of a “ veri- 
fication department.” We could have multiplied instances, but 
now let us see how it is to be carried out. 
Objectives should be well packed in a wooden box, well papered, 
and a luggage label fully addressed, attached by a string, the pack- 
age should be fully stamped and registered. 
We have fixed the fee for verification at eighteen pence, which 
can be sent in stamps or in coin, within the box containing the 
objective. It has been fixed low enough to enable students 
selecting an objective to pay it, while as there are always expenses 
connected with such an undertaking, it is hoped the balance will 
meet them—we do not wish for more. 
Upon receiving an objective for verification, the Editor will 
despatch a post-card acknowledging its receipt, giving the num- 
ber under which the measurements will appear in the next issue of 
THE NortTHERN Microscopist. Should the sender wish for a 
copy of the results before it has appeared in the Journal there will 
be an extra fee of sixpence, and the Editor in each and every case 
reserves to himself the right of publishing the results in this 
Journal. 
Upon the next page is given the form in which the results will 
appear, and it may be seen that all the information save the tests 
for definition, dependent upon errors of sphericity and chromatism 
are there shown. 
