22 THE NORTHERN MICROSCOPIST. 

if any existed. We must confess, however, that the price paid for 
an objective is, alone, no criterion of its excellence, as the incident 
mentioned on page 256, Vol. I. of this Journal will show. A glass 
may be well corrected for a small angle, and should, therefore, be 
much cheaper than one of wide aperture, where the back lenses are 
larger and stops are inadmissible. 
Both theoretically and practically there is now no doubt that 
wide apertures are to be preferred to smaller angles, but there are 
many of the old school of thought even yet, and the optician, of 
course, seeks to satisfy the idiosyncrasies of all his customers. 
Medium or small apertures seem only to commend themselves 
when great working distance is a ste gua non, and even then they 
must be constructed on a plan for giving a large anterior focus, as 
it is not a// low angle glasses which possess great working distance. 
We hope, however, to treat of this more fully in a future number. 
With all the intricacies of a trade like this we can scarcely be 
familiar, but, by keeping his weather eye open, the observer may 
find much food for reflection, and he will often discover that many 
objectives, believed to be the product of much thought and know- 
ledge on the part of different opticians, have all originally come 
: from the same factory, if indeed they are not foreign lenses put 
into an English dress. 
Being mixed up amongst thoughts correlative with all the 
| foregoing, we gladly availed ourselves of an offer to visit an ob- 
| jective factory. 
At Laurel House, North Hill, Highgate, a suburb of North 
’ London, lives Mr. W. Wray, from whose workshops a large num- 
ber of low and medium power objectives of excellent quality are 
turned out. 
In the garden adjoining his house these workshops are situate, 
so that all the operations may be under his immediate control, and 
this is further provided for by the active part taken in the produc- 
tion and correction of the lenses by his two sons. Mr. Wray caters 
for all classes of customers; wide and small apertures, expensive 
and cheap, all are produced in his factory. 
In one room we saw the formation of large lenses, such as would 
be used in the construction of the ordinary two-inch ocular, and for 
small “bulls-eye” condensers. It was in this part of the building 
also that telescope lenses were being made. 
Our interest in these large pieces of glass, however, was not 
equal to the curiosity we felt to see the manipulation of those 
fragments constituting the fronts of }ths, ~jths, q,ths, and ;';ths. 

In the next room this was going on, and at one of the benches we 
were in time to see the finishing touches given to the achromatic 
lens of a Webster Condenser, while at another bench some very 
minute lenses were being made. 


