2562 



Journal of Applied Microscopy 



to the point of effective strength the width and thickness of wooden case-frames. 

 Admission to desk cases and wall cases does not seem to be well provided for 

 in it; but for groups, special mounts, permanent large exhibits, infrequently 

 opened, it has a wide and hopeful applicability. 



In this connection it is mentioned as forming a dust-proof ctW. Examination 

 was made of the front windows of a flower store in a dusty, wind swept avenue 

 of New York city, and the assertion of the proprietor when asked as to the ade- 

 quacy of this method of protection against dust, was that " not a particle of dust 

 entered the store through the joints of the glass." These glass cases may very 

 properly receive more and more attention from museums, and Mr. Ganter (397- 

 399 Canal street, Baltimore) is desirous to introduce them into extensive scientific 

 use. 



Mr. Henry H. Hindshaw of the Albany State Museum has suggested a filter 

 device by which free access of air to the case is allowed, robbed of its dust, thus 



Fig. 76. 



dissipating the effort of the air to enter the case from all sides owing to the cir- 

 cumambient pressure, which he avers is constantly present. The question of 

 such a pressure seems apparently quite clear. In a series of experiments made 

 in the New York museum, in which Mr. J. Maher assisted, the temperature, 

 inside different cases, and under differing conditions, was found to be almost 

 invariably higher than that of the air outside, producing obviously a pressure 

 toward the case, though at moments this must almost disappear, and during 

 much of the day cannot be appreciably great. 

 Temperature inside and outside of cases : 



