HARD WICKE ' S S CIENCE - G SSIP. 



209 



geology, particularly in glacial geology. He had 

 come over to England to pursue his studies on this 

 subject, and to attend the approaching meeting of 

 the British Association. 



Parts III. and IV. of Mr. Howard Saunders' 

 " Illustrated Manual of British Birds" are published, 

 and fully maintains the high opinion we expressed 

 about it at first. 



We have received Parts I. and II. of Dr. Karl 

 Russ' "Speaking Parrots," published by L. Upcott 

 Gill. It deals with the diet, diseases, &c, of these 

 birds, and is well illustrated. 



The last number of the " Journal of the Geologists' 

 Association" contains papers on "Pleistocene Land 

 and Freshwater Mollusca," by B. B. Woodward; 

 " Elephas primigenius associated with Flint Imple- 

 ments at Southall," by J. A. Brown ; and on the 

 "Influence of Geology on the early Settlements and 

 Roads," by F. J. Bennett. 



We have received a reprint of Mr. William Cash's 

 important paper on " The Fossil Fructification of 

 the Yorkshire Coal Measures," originally published 

 in the " Proceedings of the Yorkshire Polytechnic 

 Society;" also a reprint of Mr. A. Smith Wood- 

 ward's "Synopsis of the Vertebrate Fossils of the 

 English Chalk," from the " Proceedings of the Geol. 

 Association." 



MICROSCOPY. 



Measurements by Camera Lucida. — Would 

 you kindly reply through correspondents' column the 

 following queries ? (i) In measuring with the micro- 

 scope by means of Camera Lucida. The books I 

 have state that the distance from table must be 10" 

 when the micro is horizontal. I presume that is if the 

 distance between the object and the eye-piece 

 measures 10"? (2) If I now pull the draw tube out 

 3" making the distance from object to eye-piece 13", 

 I reason that I must raise the micro until it measures 

 13" from table, is this correct ? (3) Roundly stated, 

 should the distance from table (when micro is 

 horizontal) not equal the distance between object and 

 eye-piece in all cases ? — R. W. 



New Slides. — We have received a special slide 

 of the Hessian fly {Cecidomya destructor), with illus- 

 trated descriptive sketch, from Mr. Fred. Enock. 

 Mr. Enock has devoted special attention to the life- 

 history of this notable insect, and has watched and 

 noted every change from egg to egg again, and we 

 believe it is his intention shortly to publish a full 

 account of it. The "Journal of the Trenton Nat. 

 Hist. Society" contains papers on "Freshwater Im- 

 pressoria," by Dr. A. C. Stokes, &c. 



New Method of Classifying Bryozoa.— In- 

 stead of depending upon exterior characteristics for 

 classification, the bryozoa are ground into the re- 

 quired thinness and submitted to the microscope. 

 The method of preparing these mounts is described 

 in "Science" by Mr. A. F. Foerste. The specimen 

 is ground on a Barnes' machine with emery till a 

 plane is formed, having the same direction as the 

 intended section. The successively finer grades 

 can be made very fine indeed by using polish- 

 ing powders sprinkled over a piece of plate glass. 

 Then the specimen is carefully washed, dried, and 

 glued with Canada balsam to the slide which is to 

 retain the specimen. The specimen is then ground 

 away until only a thin sheet remains fastened in the 

 Canada balsam, after which it is again smoothed, 

 washed and protected by a thin cover glass. 



ZOOLOGY. 



H. NEMORALIS VAR. SCALARIFORME. — I have to 

 record from this district a specimen of the rare shell 

 Helix nemoralis, M. scalariforme. Mr. R. Stand, 

 author of the "List of Lancashire Land and Fresh- 

 water Molluscs," paid a visit to this district in June, 

 1887, and called to see it, and pronounced it a 

 unique specimen of that variety. Mr. E. Collier, of 

 Manchester, called and saw this specimen, and pro- 

 nounced it to be one of the finest that he had the 

 opportunity of seeing. — J. Russell Wildman, Burnley, 



Planorbis dilatatus. — A short time ago much 

 interest was created among conchologists by the 

 rediscovery of P. dilatatus in a pond at Burnley, and 

 some theories were offered by Mr. T. Rogers, of 

 Manchester, as to their probable introduction to 

 Burnley. The ponds in which they were discovered 

 were the feeding ponds to a paper-mill, and to the 

 engines of a weaving shed, and their temperature is 

 somewhat above the normal, which no doubt accounts 

 for their being larger specimens than those obtained 

 from the Gorton canal. The chief weeds in the pond 

 are Potamagun crispus, Anacrhais alsinastrum, and a 

 confervoid which grows on the sides and on the but- 

 tresses of the railway viaduct which crosses the ponds. 

 I may say these are the ponds mentioned as "Marger- 

 son's Print Works," in Dyson's List, and it is doubtful 

 whether they were to be found when that list of 

 molluscs was written. Some months ago Mr. F. C. 

 Long discovered them also in the canal which runs 

 through Burnley, but the specimens were not so 

 large as those found in the ponds. These also were 

 found in close proximity to the return pipe from the 

 condensers of the engines of a large spinning mill, 

 and on examination of the embankment farther into 

 the town, in some numbers, and also extending into 

 the country for over a mile beyond the farthest mill, 

 but in smaller numbers. When these shells were 



