TRANSACTIONS OF THE SECTIONS. 233 



sand, or to rewash the sand foimuig the body of the filter ; but it was explained 

 that it was unable to wash the impmities fi-om the filter-scrapings. Neither the 

 old machines nor any mechanical means even in the laboratoiy are able to do this. 

 By cai-eful experiments, samples of the mud on the surface of the Kirkcaldy filters 

 were obtained separate from the underlying sand ; and it was found that 100 

 parts of the mud consisted of about 9o parts of diatoms, 4 parts of animalcules, 

 and 1 part of inorganic matter, beside the sarcoid matter of the diatoms from 

 which the oifensive smell of the mud is derived. The only way to recover the 

 sand from these scrapings is to allow them to lie exposed to the air for some 

 years, until the sarcoid matter is decomposed. The flinty valves of the diatoms 

 may then be removed by washing. A portion of the mud passes below the siu'face 

 into the body of the filtering-sand, and in course of years is spread through its 

 interstices and reaches even to the bottom. This mud consists almost wholly of the 

 frustules of two minute kinds of diatoms, Orthosira and Cymhella ; and by means 

 of the microscope, used sand may be at once distinguished from fresh sand by the 

 presence of these. They are easily removed by washing. 



On a Pneumatic Tramway Car. By W. D. Scoit-Monceeiff. 



On an Elevating Steam Ferry. By Wm. Simons. 



The object of this vessel is to supersede the present inclined approaches or slips 

 to'ferry stations, and therefore lessen the wear and tear in horses and haulage, to 

 enable a gre<ater traffic to be conducted with greater dispatch and economy and 

 on the same level as the adjoining quays. The valuable ground required for slips 

 is unnecessary, and the ferry-steamer is not confined to a special berth or locality. 



To effect the above objects, it is proposed to construct a steamer with a centre 

 platform of sufficient capacity for the traffic, and capable of being elevated and 

 lowered to suit the rise and fall of the tide, and thus enable the vessel to receive 

 {level with the adjoining quays) waggons, goods, horses, caniages, and passengers. 



On the Brake Problem. By James Steel. 



On Communications hetiveen Passengers and Chiards in Railway Trains. 



By "W. Stroudlet. 



On Naval Signalling. By Sir "W. Thomson, F.E.S. 



On Steam-Shi2i Resistance. By J. Evelyn Williams. 



