ZPOLOGY AND BOTANY, MICBOSCOPY, ETC. 



145 



so as to make the slide the highest part of the siphon, and the pressure 

 of the atmosphere holds the cover tight. 



This apparatus is adapted for the gas-microscope, as by a constant 

 flow of cold water the Triton can be kept in the focus of the condenser 

 for hours. 



Mapping- with the Micro-spectroscope.* — Mr. J. Deby says that 

 when mapping with the micro-spectroscope the difficulty of measuring 

 exactly the position of fine lines or absorption-bands is often great, 

 but that he finds that in most practical cases the micro-spectrum can 

 be thrown upon a sheet of white paper by means of an ordinary 

 camera lucida placed over the eye-piece of the spectroscope, strong 

 light by means of a condenser being thrown through the liquid 

 tinder examination. By means of an ivory rule, finely divided, and 

 brought back to a known line, say D, all other lines or bands may be 

 directly measured off on the rule, and, if desired, the exact results in 

 millionths of a millimetre may then be computed by any of the known 

 interpolation formulae, such as are given in Mr. Suffolk's useful little 

 book-f 



Tubes for conveying Moist Specimens, Diatomacese, &c., by 

 Post4 — J- J- M. recommends a thin membrane of gutta-percha, such 

 as is used by surgeons, cut to the required size. The joint is made 

 by dipping a camel-hair brush in chloroform, drawing it along the 

 edge, say half an inch wide, and then placing the part to be joined to 

 it before the chloroform has evaporated. If the tubes are only three 

 parts full, it will allow of a little pressure, should it occur in transit. 

 The cover can be made by rolling brown paper over a ruler or other 

 suitable form, fastening with paste, as firework cases are made, allow- 

 ing to dry, then cut to lengths required. 



* Journ. Quek. Micr. Club, vi. (1880) pp. 165-6. 



t ' Spectrum Analysis as applied to Microscopical Observation.' (Svo. 

 London, 1873.) % Sci.-Gossip, 1881, p. 17. 



Ser. 2.— Vol. I. L 



