February ll, 1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
643 
In the instrument itself there have been various 
improvements. One of those I have now before me 
is a very excellent example of the ordinary pattern 
of a student’s microscope,—one which is capable of 
having various appliances added to it, which make 
it a very useful instrument. There are two plans of 
construction which I think it well to mention, be¬ 
cause I very much hope that the direction that mi¬ 
croscope-makers will take is that exemplified in one 
of these, and which I maintain to be the right one, 
—most instruments up to the present time being con¬ 
structed on what 1 consider a wrong principle, 
mechanically and practically. In this microscope, 
which is constructed on what is called the Loss 
model,—it having been produced by Mr. l!oss, I be¬ 
lieve the grandfather of the gentleman lately dead,— 
the body or tube of the microscope is fixed at the 
bottom into an arm; then there is a transverse arm 
that is supported upon a rack stem. Now I appre¬ 
hend a very great object in all microscopes is to ob¬ 
tain steadiness in the object; that is, that when you 
look through the microscope the object shall not 
seem to dance. The reason of this dancing is that 
the eye-piece has a tremulous motion which the 
object itself has not. If the whole microscope moves 
together, and the motion is equal in every part, you 
have no apparent motion of the object. For instance, 
during the last three years, during each summer of 
which I have been using the microscope on board 
ship, I fixed my instrument well down to the table, 
if the sliip was rolling much, holding the leg of the 
table between my knees, and so fixing myself se¬ 
curely ; and during the whole of the time this instru¬ 
ment has been my companion, and I have found so 
extremely little tremulous motion, even under the 
most trying circumstances, when the steamer has 
been going at full speed against a head sea, that I 
hardly perceived any of that objectionable motion in 
the object, the microscope and my eye going together. 
If there is no motion of any one part upon the other, 
the object will remain stationary; but if the eye¬ 
piece moves more than the object itself, then the ob¬ 
ject will appear to dance. Now my friend and col¬ 
league Dr. Wyville Thomson had with him a 
microscope constructed on the Ross model, and I 
found that I could work with my instrument under 
these trying circumstances with a power about four 
times that which he could; that is to say, the tre¬ 
mulousness of mine with a quarter-inch focus, which 
is a high magnifying power, was not greater than he 
found with a lens of one inch focus. This was the 
practical proof of the superiority of the one method 
of construction over the other, and I think all who 
have any knowledge of mechanics will see at once 
the superiority of this model. All metal-work has a 
certain elasticity about it, especially a drawn tube 
such as that of which the microscope body is made ; 
the consequence is, that when the centre of move¬ 
ment is at the bottom of the tube, from which 
springs the rack upon which is placed the object- 
glass, there is the whole length of the tube to 
vibrate backwards and forwards. On the other 
hand, in this plan, which was devised by the late 
Mr. Jackson, of Spitalfields, the body is supported 
on a solid limb about the middle of its length, and a 
solid limb is carried down which supports the stage ; 
and the body being thus supported about the middle, 
the vibration is equally distributed, so that there is 
practically hardly any vibration at all. My convic¬ 
tion is very strong, that if it had not been that early 
| microscope makers had got up their patterns on 
this model of Mr. Ross’s, they would soon have 
abandoned it; but we know that when manufactu¬ 
rers once get a stock of patterns they are loth to 
change them, and I am afraid I shall not five to see 
this improved plan brought into general use. Messrs. 
Smith and Beck, however, have adopted Mr. Jaok- 
son’s model, and some of the makers who have been 
educated in their workshop have followed. I hope I 
shall not be considered to be dealing unfairly by 
other makers if I mention that the maker of this in¬ 
strument, Mr. Crouch, also makes a student’s micro¬ 
scope on the same plan, about the same size as this 
Ross model, which I consider much superior, the 
body being supported in this more stable manner. 
I mention this with the more confidence, because I 
know his instruments are now coming into general 
credit. My friend Professor Michael Foster, of 
Cambridge, lately of University College, who is now 
organizing a physiological laboratory there, has in¬ 
formed me that lie finds Crouch’s microscope a most 
satisfactory instrument. I am speaking now merely 
of the plan of construction, which I consider far 
superior, and I hope in time all makers will adopt 
it. 
The other great improvement which the micro¬ 
scope has more recently sustained is the introduction 
of the binocular principle, which is simply the adap¬ 
tation of the principle of the stereoscope. I shall 
not go into the history of the manner in which this 
was worked out, though it is very curious and inter¬ 
esting, and I have been a party to it from the very 
commencement, having in my possession one of the 
first to which it was successfully applied. We all in 
England now use the plan devised by my friend Mr. 
Wenham, and for those who, like myself, work with 
lower powers, and who are in the habit of looking 
much more at opaque solid objects than flat transpa¬ 
rent ones, the binocular is a comfort I can scarcely 
describe. The difference in the fatigue which it pro¬ 
duces, not only of visual but of mental fatigue, would 
surprise you, perhaps, but it is easily accounted for. 
When one has to estimate the form of a solid object 
with an ordinary single-bodied microscope, it is ne¬ 
cessary to focus it up and down, in order to form by 
that means an idea of the projection of one part and 
the sinking in of another. The binocular gives you 
that unmistakable representation immediately ; you 
have not to think about it at all,—you cannot help 
seeing it, any more than I can help seeing that this in¬ 
strument before me is a solid form. I therefore always 
strongly recommend a binocular microscope to those 
who are really desirous of possessing a good instru¬ 
ment ; and the cost is now so very much reduced, 
that it is really far better to incur it at the begin¬ 
ning, and to add the objectives gradually, if your 
means are limited, than to begin with an ordinary 
single-tube microscope and have to change it at a 
subsequent time. The value of the binocular is now 
becoming more and more appreciated. Several of 
my scientific friends who use the instrument merely 
as a means of research, rather laughed at me for 
my enthusiasm about it, and said they did not find 
any particular benefit in it, but one after the other 
they are gradually coming to the same view. For 
instance, last night Mr. George Busk was at my 
house, when he said he had lately had an opportu¬ 
nity of working with the binocular, and had come to 
the conclusion that he could not do without it. 
Thus much must, I think, suffice with regard to 
