*264 Journal of Applied Microscopy. 



upper edge is bent over, forming a right angle. The hnes are ruled with com- 

 mon writing fluid and then a thin coat of shellac is brushed or sprayed over the 

 entire surface. The perpendicular lines are about one centimeter apart, while 

 those which run in the other direction are nine in number and are so drawn that 

 they divide the perpendicular lines into ten equal segments. At each end of 

 these lines the percentage is indicated by figures. 



This apparatus is used in the following manner : it is grasped in the right 

 hand, by the narrow end, while the fermentation tube is held in the left hand^ 

 bulb away from the body. The gasometer is then placed between the closed 

 arm and the bulb, the bent edge resting on the top of the closed arm of the fer- 

 mentation tube. The tube is now moved to the left until the neck, connecting 

 the two arms, touches the lower edge of the tin, the perpendicular lines enabling 

 one to hold the tube upright. In this position the amount of gas can be read 

 off directly to within a per cent, or two, which is as accurate as the conditions 

 warrant. The reading should be made from the center of the tube. 



The bright tin surface acts as a mirror, and, in reading, the eye should be 

 held in line with the meniscus and its reflection. 



In working out the gas formula the amount of gas remaining after the treat- 

 ment with caustic soda is noted ; this represents the hydrogen, while the differ- 

 ence between this reading and the original (a subtraction which can be made 

 mentally) is the carbon dioxide ; e. g., let the total amount of gas be (30 per cent, 

 the second reading (after treatment with Na OH) 40 per cent., then H : CO : : 40 : 



•20 = 2:1. 



W. D. Frost. 

 Bacteriological Laboratories of the University of Wisconsin. 



Test-tube Suspender for Cleaning Diatoms, etc. 



In cleaning small quantities of diatoms, or other minute objects which 

 require repeated washings in water to remove the acid, etc., it is important that 

 the vessel in which the washings are performed — usually a test-tube — should 

 have its sides perfectly vertical, as otherwise the objects 

 tend to rest against the sides and get carried off in the 

 successive decantations. To ensure this, I find it a very 

 convenient plan to suspend the test-tubes by a U-shaped 

 piece of wire, across the base of which an india-rubber ring 

 is fixed, enclosing the test-tube. The elasticity of the ring 

 allows the tube to hang perfectly freely, and if it is set 

 slightly swinging by air currents the precipitation of the 

 diatoms is rather improved, as they are prevented from lodging against the sides 

 by the slight disturbance produced. The same device is often useful in the 

 preparation of desmids and other small objects. 



G. H. Bryan. 



