TRADE ANNOUNCEMENTS New Metal-to-Glass Seal
Bausch % Lomh Bulletin
A new metal-to-glass seal bas been developed by the Research Laboratory of the Grmcrd EIcctric Company which, because of the certainty with wh*h tight and reliable joints can be made between glass and the alloy called Fernico, has opened up many possibilities in the development of various classes.of vacuum tubes and other devices wherein leading-in wires or conducting parts must pass through gas-tight insulating seals or themselves form part of a gas-tight chamber. Fernico can be machined, forged, punched, drawn, stamped, s o l d a d , copper-brazed, and welded with a facility equal to that with which these operations can be performed on a high-grade nickel-iron. The physical characteristic of Fernico which makes possible its successful fusion with glass, is its expansion curve, which coincides almost exactly with that of certain glasses. For this reason, no stresses are set up in either the glass or the d o y when cooling from the fusion temperature. This lack of initial internal stresses in the completed glass-Fernicoseal makes the seal permanently tight and unusudv sturdv. Furthermore, no more care in cooling the combination is necessary than in dealing with glass alone.
As the result of many inquiries, Bausch & Lomb Optical Co., Rochester. New York, has prepared suggested plans for two photomicrographic dark rwms. One of these plans calls for the smallest usable space 6' X 6', for which any small rwm or closet, or even the comer of a room, may serve the purpose. The other plan is for an average-size dark room, 9' X 12'. These layouts show the suggested arrangement of sink, safelight, shelves for chemicals, plates, films, paper, table, printwasher and drain-hoards. Estimated costs for carpentry, painting, plumbing, electrical wiring, and materials are stated. The plans are printed on one side of a heavy cardboard poster, 91/r' X 13", on the other side of which the rules for using the dark rwm are printed, with a bold caption, "Knock Before Entering." Copies may he obtained onrequest.
Charts and Bulletins for Educational Purposes
men t ~ t n m e rResesrch S X d of Grmnal Motors Corboration. Detroit, directed by Henry G. Weaver amounces the availabilit; far educatiowl purposes of a list of eighteen charts and pamphlets. Those mast hkely to be usclul to teachers of chemistry &e charts No. 2 and No. 6 entitled respectively, "From all fields of science." and "&Cycle engine works like a cannon." Teachers are invited to submit their names for addition to the mailing list to receive future publications, indicating the subjects in which they are most interested. ~~~
Leitz Large Micm-Metdograph "MM-I" Catalog No. 52 B 1of E.Lei&, Inc., is an interesting publication containing numerous photomicrographs and dwelling on the latest developments in metallographic equipment. Spedal attention is invited to the arrangement for dark-field illumination by means of which detrimental reflection is avoided even in the most difficultcases. A further innovation k the arrangement by which the metallograpbic microscope serves as a fully equipped polarizing instrument for examining metal specimens, etc. Amateur Micro-Projector "Micro movies" is the term used by some amateur microscopists to describe the projection of living specimens on a screen. The introduction bv Bnwch & Lomb of a new Micro Proiector to acwmplish this-purpose a t less than half the price if the professional type follows a need expressed in numerous inquiries.
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All-Metal Vacuum Switch A new small vacuum switch, made almost entirely of steel and designed to take advantage of the absence of an arc when breaking a circuit in a high vacuum, has been announced by the General Elcchic Company. Although this new vacuum switch is only about of an inch in diameter and 11/2inches long, and can be operated by a fraction of an ounce of pressure, it is capable of interrupting as much as five horsepower as fast as thirty times a second. Designated as the Type FA-6 vacuum switch, this new device is rated at 10 amperes, 250 volts D.C. or 440 volts n.c.-r 5 amperes a t 500 volts o x .
Fixanal Preparations An illustrated folder deserib'mg the use of Fixanal preparations and a price list of preparations available may be obtained from
PfeUe& Baucr, Inc., 300 Pearl Street, New York City.
The screen is between the projector and the audience, allowing the operator to face his guests while describing the specimen. The projector operates an 110 volt, A.C. current only. It may be used with any microscope. By clipping a mounted mirror to the eyepiece tube of the microscope the image is thmwn down on paper or notebook where it may be rapidly and accurately traced.
