al 
bal 
60 J. W. Bailey on a Universal Indicator for Microscopes. — 
slide will intersect the horizontal graduation. By observing now 
the numbers at which the guide lives respectively stand, the + — 
record can be made. Sn ppose for example that the hirizeciil 
guide line rnled upon the slide intersects the verticals of the In- 
dicator at 43, while the right hand vertical of the slide cuts the 
horizontal series of numbers of the ludicator at 75; the eutry to 
made for this object in the register would be written thus 42/ 
and whenever that particular object is to be fonnd either by the 
same Indicator or any other copy of it, if the slide is placed at 
these numbers and the Indicator is properly centred, the object 
_tanst be in the field of view. In the same manner any number 
of ‘objects can be registered or found, If the slide happens to be 
so placed that both of its verticals intersect the graduated portions 
orizontal line C, D, the position of either one of them 
ill. 
ine upon the slide falls between two divisions of 
fraction of the division may be estimated with 
sufficient accuraey. b y the eye ora hand magnifier and entered 
ws the recorded position ae would mean © 
that the vertical lines of the Todicator were intersected at ith of 
a division of the scale beyond while the vertical guide line of 
the slide passed 4th of a diiioe beyond “the. number 34 of the 
horizontal scale, as nearly as could be estim: = 
It is convenient to let the lower edge of the lass slide. 
against a straight edged guide piece which can be moved paralle 
to the horizontal line of the Indicator. By pushing the slide 
along this edge, all the objects on the same horizontal can be 
found without changing the position of the guide piece. By 
moving the guide piece alittle forward or back another sweep 
across the slide may be made, and so on until every object of 
interest is foun 
By following ‘the directions above given it will be found that 
in the register. 
been employed in describing the method. It is believed that the 
explanation above given is sufficiently explicit to enable any one 
to use the Indicator; but some additional remarks will now be 
t was desired to ‘make the instrument capable of universal ap- 
plication; so simple that it could be adapted to any stage ; SO 
light and. yet so strong that it could be sent without injury by 
mail or otherwise to any distance; and lastly that the different 
copies na be perfect fac-similes of each other and reproducible 
