lii Trans. Acad. Sci. of St. Louis. 



The largest burls, which are from one to three feet in diam- 

 eter, have rows of long holes within each ring. These 

 holes are diamond-shaped in cross-section, the longer diameter 

 extending radially. Between the holes the wood fibers are 

 compressed tangentially. The speaker explained that the 

 holes must have resulted from an excessive radial pressure 

 exerted from without, probably by the bark. No holes were 

 found where the bark pressure had been released, i. e., where 

 the bark had burst. These results were not in harmony with 

 the findings as to bark pressure reached by Krabbe. The 

 speaker described the way in which these burls form by 

 excessive growth, induced by a wound or branch stump. 



Professor F. E. Nipher exhibited stereopticon slides made 

 from a large number of photographic negatives which had been 

 taken by the electric spark from a Holtz machine. The neg- 

 atives show a complete picture of the object acted upon by 

 the spark, and also show the electrical radiations in the field 

 around the object photographed. 



The plates were greatly over-exposed to light before they 

 were used. They were allowed to lie fully exposed in a well 

 lighted room for from one to nine days. The best results are 

 obtained by darkening the room when the electrical image is 

 produced. Light is found to counteract the electrical effects 

 when their action is simultaneous and also when it follows 

 the electrical exposure. The pictures are developed in the 

 dark room, by the light of an incandescent lamp. When the 

 negative begins to fog, it is token nearer to the lamp, and it 

 at once clears up. All of these methods are in total disregard 

 of all ordinary photographic procedure. Cramer's . crown 

 plates were used and the developing solution is that in 

 common use in photography. 



The result which is most interesting from a scientific point 

 of view is shown on twelve negatives which reveal ball 

 lightning effects. Ball lightning is to the electrician what 

 the sea serpent is to the zoologist. It has often been seen, 

 but never by those who are most competent to study and 

 describe it, and all efforts to produce ball lightning effects by 

 artificial means have hitherto failed. But these twelve neg- 

 atives show with perfect distinctness discharges of this 



