NATURAL HISTORY SOCIETY OF GLASGOW. 121 



0. fastigiatum in British herbaria. Mr Shaw also exhibited 

 Orthotrichum Sturmii and 0. calvescens, the former from Bowling, 

 the latter from Dailly; Dissochn s])laclmoicles, from Ben Lawers; 

 LesJcea pulvinata, in fruit, from Dailly; Leucodon morensis, in fruit, 

 from near Killin. He likewise laid before the meeting specimens 

 of Bryum Schleicheri (a var. of L. turhinatum), from Unst, in 

 Shetland, where he and Mr M'Kinlay had gathered it in 

 June, 1864. 



Mr David Bowman exhibited, under the microscope, specimens 

 of the recently discovered insect infesting the buds of the black 

 currant, showing an additional stage of its development; also, a 

 species of acarus found on the same buds. Mr Bowman likewise 

 submitted to the meeting a new form of an object-finder for the 

 microscope, which is constructed by affixing to a glass slide-bearer, 

 three inches -long, four scales, each an inch in length, divided into 50 

 degrees. These are placed along the central portion of the upper 

 and lower edges of the bearer, and across the bearer, half an inch 

 distant from each end. Two lines are engraved on the stage of 

 the microscope at right angles to each other, running across the 

 aperture of the stage, these lines intersecting each other on the 

 field of view. These form lines of longitude and latitude. The 

 slide to be examined is then placed on the bearer, and put under 

 the microscope; and if any minute object, such as a diatom, comes 

 into the field which it may be desirable to see again, the points at 

 which the degrees on the scales are cut by the intersecting lines 

 on the stage may be recorded for future reference. This may be 

 done in a fractional way. If, for instance, the perpendicular line 

 on the stage cuts the horizontal scale at degree 32, and the hori- 

 zontal line cuts the perpendicular scale at degree 34, they may be 

 set down thus — 32.34. At any future time the object may be 

 found by placing the slide on the bearer, and bringing it to the 

 position in which the lines on the stage cut the recorded degrees, 

 and if the observation has been correctly taken and recorded, the 

 object will be found in the field of view. Mr Bo-mnan also 

 explained another way of finding out an object when the stage of 

 the microscope is fitted with intersecting lines as already de- 

 scribed. In order to examine a slide, it is placed on the stage, 

 and pushed up by the sliding bar on the stage, or lowered with it, 

 as the case may be, so that the slide may be parallel to the 

 horizontal line on the stage. When an object is found in the 



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