696 CURRENT TOPICS. [J. F. I.

Dus t H a z a r d in the Abras ive I n d u s t r y . - - T h e conviction is g rowing a m o n g experts , that workers in dus ty t rades are espe- cially liable to tuberculosis . The subject has been t rea ted in a bulletin by Professor Wins low, of the Yale Medical School, assis ted by L. and D. Greenburg of the U. S. Public Hea l th Ser- vice and publ ished as Repr in t 53 ° of tha t service. Ex tens ive examina t ions were made of two large factories des ignated respec- tively as B and C, the former employing 2ooo hands, of which 40o are women. In both cases much defect was found in the methods of avoid ing dust. Whi le ord inary inspect ion in one of the fac- tories in which some installations had been made with a view of improv ing the condit ions some benefit appeared, the analysis of the air did not confirm the opinion. Compar i sons are given be- tween these factories and those of other o'ccupations in which dus t is produced in considerable amount . F r o m the figures it seems tha t the am oun t of dust ranges f rom 2.37 mgms. of solid particles in IOO cubic feet of the air of a good polishing shop, to 78o.5 mgms. in the same volume of air in factory C. I t is noted that while the total dust in the air of a carpet and blanket mill is higher than mos t of the other industr ies given in the table (such as pot tery , asbestos, tobacco, steel gr inding) , the inorganic mat - ter in the texti le dust is the lowest. The bulletin concludes with the s t a t emen t that es tab l i shments in which abras ive mater ia ls are made may present condit ions in regard to aerial dust un- equal led in any other industry, and tha t the subject is an impor- tan t one in industr ial hygiene. I t would be wor th while to inquire whe ther any form of ga s -mask can be utilized for the protect ion of the worker . H . L .

H e a r t w o o d and Sapwood. (Technical Notes, Forest Products Laboratory, I 9 1 9 . ) - - I n over 3oo,ooo tests which have been made at the Fores t P roduc t s Labora to ry , Madison, Wis. , on the var ious species of wood g rown in the Uni ted States, no effect upon the mechanical p roper t ies of wood due to its change f rom sapwood into hea r twood has ever been noticed. A n y difference in the s t r eng th of hea r twood and sapwood can usual ly be explained by the g r o w t h and densi ty of the wood.

In other than mech'anical properties, there are differences be- tween hear twood and sapwood which have an impor t an t bear ing on their use for var ious purposes . T h e sapwood of mos t Amer i - can species is cons iderably less res is tan t to decay than the hear t - wood, and where the wood is used without preservative treatment in s i tuat ions which favor decay, the" sapwood is l ikely to have a much shor te r life. In these par t icular cases, therefore, s t r eng th requ i rements m a y have an indirect bear ing on the choice be tween h e a r t w o o d and sapwood, inasmuch as wood infected with decay is likely to have its strength properties, particularly that of shock resistance, g rea t ly reduced.