1900] MICROSCOPICAL JOURNAL. 89 



single-layered, spithclium, the massing- of sub-spidermal 

 parenchyma, and the finely-formed crystalsscattered 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- 

 ganic matter — the latter being found in greater or less 

 quantity, in almost every case. But on closer examination 

 with higher 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 safeguard is not chemical solvents, 

 but frequent and thorough inspection and cleaning-. — J. S. 

 Dales. 



Wanted. — Earth containg diatoms from Redondo Beach 

 for a European subscriber who offers cash, or, in exchange, 

 Hungarian diatomaceous 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. 



