300 EXPERIMENT STATION RECORD. 



A crosscut excavating- machine for drainag-e ditches (Engin. News, 54 (1905), 

 No. 10, p. 250, fig. 1 ).— This is an illustrated description of a new type of self-propelling 

 excavator, with the peculiarity that the cutting is done by buckets moving trans- 

 versely to the line of the canal, on a steel guide frame or template of such shape and 

 proportions that the buckets give at once the desired finished shape to the bank of 

 the canal. 



"With a ditch 16 ft, wide on the bottom, and 6 ft. deep, having side slopes of 1 to 

 1, the machine frequently cut 180 lin. ft. in less than ten hours, the machine being 

 subject to ordinary delays. This is equivalent to between 800 and 900 cu. yds., and 

 was accomplished with the consumption of not more than a ton of coal. This 

 machine weighed 30 tons and had a vertical boiler and a 20 H. P. engine with cyl- 

 inders 7 by 10 ins., operating two buckets of If cu. yds. capacity. The only labor 

 required comprised the engineman and fireman on the machine, and one man with 

 team to attend to the laying of the track. . . . 



"Among the advantages claimed for this new machine are a reduction in power 

 and labor as compared with a dipper dredge of the same capacity, while the banks 

 are left with the proper slope and in better condition to prevent slides and to give 

 the full capacity of flow for the channel." 



Contribution to the biochemistry of sewaga purifiation: The bacteriolysis 

 of peptones and nitrates, S. DeM. Gage (Technol. Quart., 18 (1905), No. 1, pp. 

 5-39).— This article reviews the literature of the subject of the biochemistry of sew- 

 age purification, giving a bibliography containing 113 references, and reports experi- 

 mental data obtained in investigations made at the Lawrence Experiment Station on 

 the processes of ammonification, denitrification, nitrate production, a reduction of 

 nitrates to ammonia, distribution of ammonifying and denitrifying bacteria in sewage 

 and sewage effluents, and on the relation of peptonization to other biochemical 

 functions. 



Studies were made of the behavior of 30 pure cultures of bacteria common in 

 sewage and sewage effluents in two solutions (1) 0.1 per cent Witte's peptone solution 

 containing about 14 parts of organic nitrogen per 100,000, and (2) 0.1 per cent of 

 Witte's peptone in distilled water, diluted to three different strengths at different 

 periods of the investigation, and containing nitrogen as potassium nitrate equivalent 

 to 2.7, 6, and 22.5 parts per 100,000. The methods of chemical analysis used are 

 described. 



Summarizing the results, the author states that the problem of sewage purification 

 is mainly a question of the bacteria which transform (render innocuous) the nitrog- 

 enous matter. 



"From the results obtained in this study it becomes possible to state definitely that 

 bacteria common in sewage purification are able to produce ammonia from organic 

 matter, to reduce nitrates to nitrites, to ammonia, and probably to elementary nitro- 

 gen, to liberate nitrogen from solutions of organic matter either with or without the 

 presence of nitrates or their reduction products, and also to fix atmospheric nitrogen 

 under the same conditions — all of which reactions have been noted by other 

 observers, but about which there has been more or less controversy. 



"Many sewage bacteria probably also produce the lower oxids of nitrogen as 

 reduction products of nitrates, which oxids may play an important part in the fur- 

 ther decomposition of the organic matter in solution, either through catalytic action 

 or by direct chemical reaction. Furthermore, certain of these bacteria may perhaps 

 produce an oxid, or at least a compound of nitrogen intermediate between nitrates 

 and nitrites, which has apparently not been noted hitherto. 



"The amount of ammonia produced by the different cultures has ranged from 

 none to 18 parts per 100,000, and the rate of ammonification has varied considerably, 

 some of the cultures reacting as early as the fourth day, while other cultures, which 



