2454 



Journal of Applied Microscopy 



(c) In pus, blood, etc., you can mix the above stain with an alcoholic methy- 

 len blue solution. 



The gain is in quickness, simplicity, cleanliness and excellent results in stain- 

 ing, the Flagelhe being seen while the field is kept clean and unstained. 

 Rogers Park, Chicago. V. A. Latham. 



A New Sling Psychrometer. 



A couple of years ago my attention was called to the desirability of having 

 something a little better than the ordinary sling psychrometer for use in my 

 classes in botany. As is well known, it requires a good deal of free space to 

 enable one to manage the ordinary sling psychrometer without striking some 

 object. Those of the ordinary pattern which we have used in the field and also 

 in the laboratory are invariably broken after a short time. The suggestion was 

 made that the whirling of the thermometers might be accomplished by some 

 mechanical means, and after a number of trials, and the manu- 

 facture of several instruments, the one here shown in the figure 

 was made. It consists of a handle, shown at the bottom (Fig. 1), 

 and to this is attached a bevel cog-wheel which works in another 

 smaller wheel, turning the upper portion of the apparatus. 

 To this upper portion are attached the two thermometers, the 

 one having its bulb covered with cloth and the other free. By 

 wetting the cloth on the one thermometer and then rapidly 

 turning the crank attached to the wheel, a very rapid motion 

 is given to the frame which carries the two thermometers. In 

 many trials made with this apparatus, it has been found that 

 the effect of this rapid rotation is exactly the same as that 

 produced by the slinging motion of the ordinary sling psychro- 

 meter. The advantage of this little apparatus is that it can 

 be used without danger of breaking the thermometers. This 

 form is of still greater advantage in work in the field, especially 

 in forests and thickets. It is not at all difficult to obtain the 

 relative moisture of the air in the middle of a thicket by this 

 instrument, whereas it would be utterly impossible to do so by 

 the use of the ordinary sling psychrometer. 



In making the instrument thus far I have found that the cheapest plan is to 

 purchase a " Lyon Egg Beater " and to have a mechanic remodel the upper 

 portion in the way indicated. I have a number of such instruments which cost 

 me a little less than two dollars apiece, and they are much more serviceable than 

 my sling psychrometers that cost twice as much No doubt a skillful mechanic 

 can make a neater looking instrument than these made out of transformed egg- 

 beaters, but it will probably not do any better work. 

 University of Nebraska. CharLES E. BesSEY. 



Fig. 1. 



