xxvi Trans. Acad. Sci. of St. Louis. 



Mr. G. Pauls laid before the Academy a branch of a small 

 hackberry (Celtis) which had become completely covered 

 with the small nodular galls frequently borne in smaller 

 quantities by the hackberry, and called attention to the fact 

 that in this particular case the natural enemies of the gall- 

 forming creatures seemed to have been absent, allowing the 

 unusual multiplication. 



Dr. Albert Habermaas, of St. Louis, was elected to active^ 

 membership. 



Three persons were proposed for active membership. 



March 18, 1901. 



President Engler in the chair, forty-three persons present. 



Professor Edward H. Reiser delivered an address on 

 Progress in the science of chemistry during the nineteenth 

 century.* 



Professor F. E. Nipher exhibited pieces of pine board a 

 foot square, showing the tracks of ball lightning discharges 

 upon them like those formerly described by him in No. 6, 

 Volume X, of the Transactions of the Academy. The dis- 

 charges formerly described had been formed on a photo- 

 graphic film. The balls were very small, and wandered over 

 the plate, leaving a track of metallic silver in their wake. In 

 the present instance the balls were much larger, and they 

 burned a deep channel in the wood. They are formed at the 

 secondary spark gap of a coil. The terminals are pointed 

 and are under control, so that the gap may be changed in 

 length. To start the balls, the pointed terminals are put upon 

 the wood surface, so near that the surface carbonizes some- 

 what, after which the gap is made longer. These balls travel in 

 either direction, when a direct current is used with a Wehnelt 

 interrupter. This differs from the results reached on the 

 photographic film with the Holtz machine. There the balls 

 came from the cathode. Even when they originated at isola- 

 ted points on the film, they traveled away from the cathode. 



In the present results, the balls have been caused to orig- 



* This address was printed in full in Science, n. s. 13: 803-9. 1901. 



