May 1, 1866.] 



SCIENCE-GOSSIP. 



113 



1858, and that only on one occasion, all other search- 

 ings in the same locality proving fruitless ; and also 

 near St. Michael's Mount, Cornwall, from which 

 locality I have had forwarded to me one very in- 

 ferior frustule of Tox. insignia. Tox. Gregoriaiui, 

 the most beautiful species in the genus, has, so far 

 as I know, not been found anywhere except on the 

 Northumberland shore, and I beg to request all the 

 readers of the Gossip who make shore gatherings, 

 to search during the present spring, summer, and 

 autumn, on their respective coasts for the diatom 

 which is so excellently represented on page 87. 

 Toxonidece of the species Gregoriaiui and insignis 

 are only found in Northumberland a little above low- 

 tide mark, and they are generally associated with 

 other marine forms. Should any be found, I shall 

 be glad to exchange slides or gatherings. — T. P. 

 Bark-as, Newcastle-on-lgne. 



Glass Cells. — To make them from glass-tubing, 

 it is necessary to slice them with a slitting-wheel 

 and diamond-dust ; this, however, is out of the 

 reacli of most microscopists. I have adopted the 

 plan suggested in Carpenter's work on the micro- 

 scope, viz., cementing a piece of glass to a perforated 

 brass plate with shellac, and knocking out the central 

 portion. I have several plates with holes, ranging 

 from I to | inch in diameter. The brass plate should 

 be the size of a glass slide, viz. 3 in. by 1 in., and 

 not less than T V thick ; the hole should be perfectly 

 central, in order that the cemented glass may be 

 placed on the turn-table, and a ring or series of 

 rings scratched upon it with a diamond ; the centre 

 may then be knocked out with a small steel hammer 

 and finished off with a round file. Cells varying 

 from the rtu to i inch in depth can be readily 

 made by this method. — Fred. Kittou, Norwich. 



MICROMETRIC TABLES. 



1. Table for the Conversion of French Millimetres into Decimal Parts of an Englisb Inch. 



2. Table for the Conversion of Parts of an English Inch into French Millimetres. 



A metre = 39-37079 inches. 



E. SWANSBOKOTJGH. 



