3o6 



SCIENCE-GOSSIP. 



packed in one box, and the condenser and other 

 parts in another. 



Major Battersby's arrangement for the generation 

 of electricity was indeed an ingenious one. He says : 

 " The pulley of a small dynamo was connected by 

 means of a leather strap with the back wheel of a 

 specially constructed tandem bicycle. The required 

 velocity for the dynamo was thus obtained, and our 

 procedure was as follows : Having carefully adjusted 

 the circuit with the storage battery, and also with 

 the voltmeter and ammeter, my warrant officer took 

 his position on the seat of the bicycle and commenced 

 pedalling. When 15 volts and 4 amperes were 

 registered, the switch close to the handle of the 

 bicycle was opened, and charging of the battery com- 

 menced. As the resistance became greater, a sensa- 

 tion of riding uphill was experienced, and the services 

 of an additional orderly «ere requisitioned for the 

 front seat. This bicycle practice was generally 

 carried out in a shade temperature of 110° Fahr. , so 

 that at the end of half an hour we unanimously 

 agreed that some other form of scientific amusement 

 was desirable. The switch now having been turned 

 off before pedalling ceased, in order to avoid any 

 discharge from the battery, the machine was brought 

 to a standstill." Major Battersby invariably used 

 glass sensitised plates. The temperature of the 

 water employed in development being high, and ice 

 being unobtainable, fine details upon the negatives 

 had to be sacrificed. As a rule development was 

 done at three o'clock in the morning, that being the 

 coolest part of the day. 



After the battle of Omdurman 121 wounded 

 British officers, non-commissioned officers, and men 

 were brought to Abadieh. Of that number there 

 were twenty-one cases that could not be diagnosed 

 accurately by ordinary surgical means, and of these 

 the presence or absence of a bullet was in twenty 

 instances proved by the X-rays. The odd case was 

 that of a shot in the lung, so severe that at the time 

 it was not considered justifiable to examine. 



In many instances X-ray observations liave materi- 

 ally assisted the dentist. Teeth are more opaque to 

 the rays than bone, hence a radiograph shows clearly 

 the teeth distinct from their surroundings. Small 

 celluloid sensitive films, about i inch by J inch, are 

 used, wrapped in black paper and then enclosed in 

 thin sheet rubber. They are placed inside the 

 mouth, and held close to the teeth by the tongue. 

 Exposure and development of the films are made in 

 the usual manner. Dr. KnoUe's instrument, the 

 dentiaskiascope, for examining the teeth, consists of a 

 small fluorescent screen in an aluminium case, so 

 placed that the screen-image is reflected upon a 

 mirror, which the operator views through a tube. 



We are indebted to Mr. A. C. Cossor, of 67 Far- 

 ringdon Road, London, for use. of original prints and 

 permission to reproduce them, for figs. 25 and 26 in 

 this number. The safety-pin shown in fig. 25 was 

 used to secure a bandage. 



( To be coiic/iided next month. ) 



A HISTORY OF CHALK. 



By Edward A. Martin, F.G.S. 



{.Continued from page 235.) 



'\^/'ITH the progress of geological science, less 

 prominent beds in a system receive more 

 detailed examination, with the result that greater 

 importance attaches to certain minor beds than was 

 formerly the case. At one time, in the case of the 

 Cretaceous now before us, it was suflScient to classify 

 the subordinate divisions thus: — (I) Chalk with 

 Fhnts ; (2) Chalk without Flints ; (3) Chalk Marl ; 

 (4) Upper Greensand ; (5) Gault. 



A more explanatory and detailed table is now 

 necessary, and we have to consider each of the 

 formations given below : — 



Faxoe Limestone. 

 Pisolitic Limestone. 

 Maestricht Beds. 

 Zone of Beleni-tiitella inucrojiata. 

 ,, ,, Marsnpites. 

 ,, ,, Micraster cor-anguinmn and 



M. cor-testndiimrhini. 

 ,, ,, .ffi;/a;j-fc;-//««z(j-( Chalk Rock) 

 , , , , Terebratulina gracilis. 

 ,, ,, Rhynconella aivieri. 

 ,, ,, Inoceratniis labiatus (Mel- 

 bourne Rock). 

 ,, ,, Beleviniiella fUna. 

 ,, ,, Ainmojiites rhotomagensis 

 ,, ,, Holaster sub-globosics (Grey 

 Chalk), with Totternhoe 

 Stone at base. 

 ,, ,, AiHjHonites variant. 

 ,, ,, Phcoscyphia vieandrina 



(Chalk Marl). 

 ,, „ Chloritic Marl. 

 ,, ,, Pecten asper. 

 ,, ,, Avinionites infiatns. 

 (including a contemporaneous portion 

 of the Hunstanton Limestone, or 

 " Red Chalk," and theBlackdown 

 Greensand in Dorset and Devon). 



Dan IAN. 



Senoman. 

 (Upper Chalk) 



TURONIAN. 

 (Middle Chalk) 



Cenomanian. 

 (Lower Chalk) 



Albiax. 

 (Upper Green- 

 sand) 

 Albian. 

 (Gault) 



The division of the beds into those which contain 

 flints and those which do not has now completely 

 broken down ; since, as we shall see, there are beds 

 in the Upper Chalk which contain no flints at all, 

 whilst on the other hand there are beds of the 

 Lower Chalk, as in Yorkshire, where tabular flints 

 are a prominent feature. It is custoinary now, 

 wherever possible, to divide strata into zones, these 

 being named after some fossil, either peculiar to the 

 zone or, at any rate, very prominently associated with 

 it. This system of nomenclature is especially valuable 

 in the case of the Chalk, since names based on purely 

 lithological distinctions are quite valueless when an 

 attempt at correlation is made with beds of similar 

 age in other lands where there is no resemblance 

 to chalk at all. This system, first introduced by 



