1900] MICROSCOPICAL JOURNAL. 89 



sing-le-layered, spithelium, the massing- of sub-spidermal 

 parenchyma, and the finely-formed crystals scattered abun- 

 dantly in various parts of the section. — R. H. Ward. 



Muddy Deposit Inside of Steam Boilers. — These de- 

 posits vary in appearance and composition according- to the 

 water and the conditions attending-, even clear well water 

 being- not exempt. This specimen was removed from a 

 boiler in constant use for power purposes, before becoming- 

 solidified into crust or "scale." On cursory view, the ap- 

 pearance is much like some very fine sand, mixed with or- 

 g-anic matter — the latter being- found in g-reater or less 

 quantity, in almost every case. But on closer examination 

 with hig-her power and condenser,and also with polariscope 

 and paraboloid, it will be found to be of different character. 

 What takes place in ordinary course seems to be this : the 

 heat precipitates salts from solution in the water,and these 

 settling- to the lowest point cover the surface of the inter- 

 rior of the steel of the boiler, and after a time prevent its 

 contact with the water. If neglected the deposit fuses or 

 "bakes," and often becomes very hard and difficult to re- 

 move. The furnace fire overheats the boiler shell at that 

 point, where without water contact, and finally "burns" it. 

 The steel of the shell loses its tinsile strength, becoming- 

 ■"crystallized" and brittle. If nothing- more serious occurs, 

 the plant or factory must be shut down while the boilers 

 are "patched," and a patched boiler must usually soon be 

 replaced. The surest safeg-uard is not chemical solvents, 

 but frequent and thoroug-h inspection and cleaning-. — J. S. 

 Dales. 



Wanted.— Earth containg- diatoms from Redondo Beach 

 for a European subscriber who offers cash, or, in exchang-e, 

 Hungarian diatoraaceous material from St.Peter .C. W. S. 



Slides.— The distinguished diatomist. Dr. Grunow, has 

 presented a very large collection of slides to the Imperial 

 Natural History Museum at Vienna. A careful prepared 

 selection of microscopic slides made by the late W. T. 

 Suffolk has been given to the Royal Microscopical Society. 



