October 19, 1917] 



SCIENCE 



387 



more satisfactory than one which was wet 

 when introduced into the dish. The water on 

 the needle would promptly unite with the sur- 

 face water in the dish, and several specimens 

 would then be lifted from the dish in nearly 

 every case, unless previously puffed away with 

 the breath. But by wiping the needle, the in- 

 dividual plant desired can often be lifted out 

 even if others are so near as to nearly touch 

 the selected plant. 



The dehydration dishes within the crystal- 

 lizing pans proved very satisfactory, and per- 

 mitted the continued cultivation of the par- 

 ticular strain under observation for a con- 

 siderable period. Frederick H. Blodgett 



Texas Agricultukal and Mechanical Colleqi, 

 College Station, Texas 



two methods of orientation of small 

 objects in paraffin 



The following method is applicable to all 

 objects which are sufficiently small to adiuit 

 of embedding in watch crystals. It has been 

 found practical and easy and is given here in 

 the expectation that it will be of assistance 

 to others. 



"Watch crystals of the Syracuse type with 

 flat bottoms are employed. On the bottom, 

 parallel lines about 2 mm. apart are ruled with 

 a diamond. These are then scraped out with 

 a coarse needle, the sharp edges being broken 

 off and the lines widened to form open grooves. 

 The watch crystals should be washed to re- 

 move the small particles of glass and are then 

 ready for use. The watch crystals are pre- 

 pared for embedding by coating the interior 

 with a film of glycerin as usual, but care must 

 be taken to rub the glycerin into the lines. 

 When infiltration is complete, the watch crys- 

 tal containing the objects is removed from 

 the oven and the bottom slightly chilled by 

 contact with cold wafer. It is then placed 

 on the stage of a binocular microscope and 

 the objects oriented with a warm needle, so 

 that the plane of section desired shall be 

 parallel with the lines and normal to the bot- 

 tom of the watch crystal. As soon as the 

 paraffin on the bottom has cooled sufficiently 

 to hold the objects in place, the entire mass 



is cooled with water in the usual manner. In 

 orienting the objects it is found that the lines 

 on the bottom of the watch crystal show more 

 distinctly by transmitted than by reflected 

 light. The block when removed shows on its 

 lower surface minute parallel ridges which 

 enable accurate and easy orientation when 

 mounted on the object carrier of the micro- 

 tome. The block should of course be placed 

 in the microtome with the ruled surface up- 

 wards and then arranged with the lines par- 

 allel with the edge of the knife and the sur- 

 face at right angles to the direction of motion, 

 that is horizontal in the ordinary vertical 

 type of Minot microtome, vertical in the hori- 

 zontal type. 



A second method, or variation of the method 

 given above, is to rule the parallel lines on 

 the watch glass with a " china-marking " 

 pencil. These lines, even though the glass 

 is thoroughly coated with a glycerin film, will 

 come away with the paraffin block and may 

 be used as orientation lines. This method 

 may also be used for numbering or otherwise 

 marking paraffin blocks. 



Jas. a. Nelson 



Bureau of Entomology, 

 Washington, D. C. 



the aurora borealis 

 To THE Editor of Science: The display of 

 the aurora borealis mentioned by your corre- 

 spondent, Mr. Thomas Byrd Magath, in Sci- 

 ence, No. 1186, as seen at Fairiwrt, la., on the 

 ninth of last August at about 8.45 (Central 

 time?) was also observed by the writer and 

 others from a yacht anchored at Thimble Is- 

 lands (Stony Creek), Corm., at about nine, 

 75th meridian time, of the same evening. The 

 display was quite brilliant, although the 

 streamers did not reach much above 50° in 

 altitude. The region of greatest brilliancy was 

 about N. 25° W., true. 



On August 14 at about the same time a 

 more brilliant display was seen at Stonington, 

 Conn. (Lat.41° 19'). The illumination reached 

 much further to the eastward and the stream- 

 ers were higher. At times masses of pale light 

 detached themselves from the general illumi- 



