Constituents of Thames Mud. By Lionel 8. Beale. 5 



with here and there black particles of coal or carbon, will be seen. 

 By mixing a small portion of mud with a considerable qnautity of 

 water, stirring it up, and then pouring off the upper part of the 

 fluid after allowing a few seconds for the subsidence of the heaviest 

 and coarsest particles, a deposit may be obtained in a state fit for 

 examination under tolerably high magnifying powers, and if the 

 process be repeated again and again, the mud may be separated 

 into several portions differing from one another in density and in 

 the coarseness of the gritty particles. But this plan is found not 

 altogether satisfactory, for many of the organic substances in the 

 mud are only imperfectly seen, while it will be impossible for the 

 observer to form any idea of the relative proportions of the various 

 constituents of the mud thus divided into separate portions differing 

 from one another as regards the size and lightness of the component 

 particles. 



After having tried many different methods of investigation, I 

 found that admixture with an equal quantity of glycerine afforded 

 the best results. In this process the specimen can be kept for a 

 length of time without undergoing change and be submitted to 

 examination at intervals. The refracting property of the glycerine 

 enables the observer to make out details of structure which could 

 not be seen in specimens immersed in water, while in each specimen 

 almost all the constituents of the mud are rendered clearer and 

 more distinct. 



Another important advantage is gained by this method of 

 examination, inasmuch as the observer is able to form a notion of 

 the relative amount of the several substances in each specimen 

 examined, and also the relative amount of each in any given 

 specimen. By this plan every constituent of the mud may be 

 seen in one preparation, and specimens prepared in this manner 

 have the additional advantage of preserving their characters for 

 many years without change. 



If a portion of the mud is simply mixed with water and then 

 stirred up, the heavier particles allowed to settle while the lighter 

 ones are poured off into another vessel and then allowed to subside, 

 a very wrong idea may be formed of the number of the lighter 

 substances present, because nearly the whole of these in the quantity 

 of mud operated upon may be separated, and the microscopical 

 specimen would in that case appear as if it consisted almost entirely 

 of this one class of constituent particles. 



This paper is based upon the results obtained by the micro- 

 scopical examination of twenty-five sj)ecimens of mud from various 

 banks between Gravesend and Chelsea taken under the direction of 

 Dr. Collingridge, the Port of London Sanitary Officer, in the coarse 

 of an inquiry undertaken at the request of the City of London for 

 the purpose of obtaining evidence to bring before the Eoyal 



