34 REPOKT OF NATIONAL MUSEUM, 1893. 



of common Aviiidow ^lass, which is somewhat irieguhir in its surfaces, 

 enough small openings occur arouud the edges for the escape of 

 gases, so that the somewhat unsightly vent-hole, usually made in 

 hermetically sealed jars to allow the escape of gas and the introduc- 

 tion of alcohol without removing the luting, is dispensed with. 



The most serious difficulty, however, has not been in regard to the 

 cover, but rather in securing at the front of the jar a face sufficiently 

 smooth and well polished to display the specimens clearly and without 

 distortion. Some of the samples made for us by the glass maiuifac- 

 turers had this surface polished on the buffing wheel; but the grinding 

 was not sufficient to remove the inequalities in the glass, and the cor- 

 ners, furthermore, are not rectangular, but rounded to such a degree 

 as to cause some distortion of the specimens. Besides this, these are 

 irregular and unsightly, and even to secure this imperfect result the 

 glass is so thick that its transparency is somewliat impaired. This 

 method of polishing the front surface of the receptacle has been used 

 also in Euroi)e. It is an alleviation l)ut not a remedj^ for the evil, 

 and, furthermore, is exceedingly expensive and beyond the reach of 

 a museum which has to provide for a large number of wet prepara- 

 tions. Jars of this type, made in Edinburgh, are used in the Army 

 Medical Museum in Washington. The cost of these jars, 9 by 12 inches, 

 at the factory was about $105 a dozen. A firm in this country' tried to 

 produce jars somewhat similar, but was unable to make them at this 

 price. 



Every important factory in the United States which would under- 

 take work of this class has been consulted, and Mr. Benedict w^as 

 sent on a special mission to visit them and study in person the possi- 

 bilities. He soon became satisfied that in the present state of the 

 glass-blowing industrj' nothing more can be done with blown jars, 

 and began investigations in another direction. 



Experiments have been made by Mr. Benedict with a view to the 

 possibility of building receptacles out of plate glass. Something of this 

 kind had already been tried in Germany, with receptacles in metal 

 frames, and constructed on the i)rinciple of an aquarium tank. The 

 2)lan adopted here has been to dispense with entirely metal, and 

 to use silicate cements which are insoluble in preservative tiuids, and 

 which unite so closely with the glass as to become, practically, a part of 

 it. The recipes for these cements used are, unfortuimtely, the property 

 •of private individuals. In the process of manufacture the recepta- 

 cles are exposed to a heat of 350"^ F. for several hours. It is impossible 

 at the time of writing to say with certainty that these experiments have 

 been successful, although one large jar has been filled with alcohol and 

 specimens for eleven months and twelve others for six months. In jars 

 of this particular form the top is made of two pieces of plate glass, the 

 lower one being smaller, and so attached to the other as to form a 

 shoulder all around; and the cover thus formed is luted to the opening 



