io6 



HARD WICKE ' S S CIE NCE- G O SSIP. 



was Blackmore, a celebrated performer on both tight 

 and slack rope, who on several occasions suspended 

 himself by the neck and imitated the struggles of a 

 dying man, but at last performed the reality, and 

 was greatly applauded. The other was Sam Scott 

 " the American Diver," who erected a tall mast on 

 Waterloo Bridge, with a boom on which he performed 

 some antics, and then dived from a fearful height into 

 the river. One of his tricks was an imitation of the 

 popular Monday morning Old Bailey performance, 

 which at last he did perfectly. 



It was generally supposed that in these cases the 

 rope slipped and compressed the larynx, but Dr. 

 Gross's experiments suggest another explanation. 

 Had the rope slipped as supposed, the athletic 

 expert, finding himself in danger of suffocation, would 

 instantly have grasped the rope and supported 

 the weight of his body as at the conclusion of his 

 ordinary performance, but if he suffered the gradual 

 swooning described by Dr. Gross, he might insensibly 

 pass the stage of strong effort and slowly die, 



Police Telegrams.— New York is supplying a 

 lesson in police organisation by adopting a com- 

 prehensive system of telegraphic communication 

 between all the police stations of the city. The 

 calls are self-recording, the system of the Herzog 

 Teleseme Company being adopted in preference to 

 the evanescent telephone. 



A Hint to Teachers. — All who are practically 

 acquainted with the working of our schools, whether 

 they be what are called " High Schools " or Board 

 Schools, or any other schools, will agree with me in 

 concluding, that the microscope is not doing the work 

 there that it should do as a general educator. Too 

 much of mere books, mere verbiage, mere rote work, 

 and too little of direct knowledge generally prevails. 

 Scarcely a school can be found in which the 

 microscope does any teaching at all. 



In large schools it is difficult to use an ordinary 

 table microscope, on account of the time that must be 

 consumed in showing objects to the pupils one by one, 

 and the solar microscope or lime-light microscope 

 demands costly arrangements. But I think something 

 might be done by adopting the simple device of giving 

 an occasional collective lesson on some selected object 

 with black-board or diagram illustrations, and then 

 placing the actual object under a microscope (a small 

 cheap one with but moderate power would be 

 sufficient), and allowing the good children to have a 

 peep at the real thing on their way in or out of school. 

 Making such exhibition a reward for good conduct 

 would greatly add to the current valuation of the 

 show, and the general interest in the instruction it 

 would carry. Even where there is no intrinsic 

 interest or pleasure in any act, it acquires a conven- 

 tional value if it is treated as a privilege or a reward. 



This is not limited to children. Full-grown men 

 grumble loudly on being compelled to sit on a jury, 



but make huge efforts to obtain the privilege of sitting 

 in the House of Commons. 



The Elements in the Sun. — Messrs. Hutchings 

 & Holden believe that they have found good reason 

 for placing platinum on the list of metals which the 

 spectroscope has found in the sun. They detect 

 sixteen coincidences of the solar lines with those 

 artificially obtained. They confirm the presence of 

 bismuth, cadmium and silver which other observers 

 have considered probable, but are doubtful concerning 

 cerium, lead, molybdenum, veranium and vanadium. 

 They are satisfied concerning carbon, which was 

 formerly described as not found. For reasons I 

 stated in " The Fuel of the Sun," chapter xiii., I doubt 

 the possibility of fairly demonstrating either the 

 existence or the non-existence of the non-metallic 

 elements by means of the spectroscope. During the 

 twenty years that have elapsed since that chapter was 

 written a great deal of spectroscopic work has been 

 directed to such investigation, and the contradictory 

 results that have been obtained, especially in reference 

 to oxygen, confirm my early scepticism. With the 

 thin sharply-defined lines of the metals the case is 

 quite different. 



Action of Caffeine. — F. Coppola has recently 

 made many experiments on the action of Caffeine on 

 both warm and cold-blooded animals. He concludes 

 that it does not belong to the same pharmacological 

 group as digitalin, because it acts on the heart and the 

 nerve-centres, whilst digitalin and some of its deri- 

 vatives act exclusively on the heart. He asserts that 

 both strengthen the heart's action by stimulation of 

 its muscular tissue, but they act differently on the 

 frequency of the beat. The chief difference is that 

 caffeine causes dilatation and digitalin contraction of 

 the blood vessels. 



Readers of the above should distinguish between 

 " strengthening the heart's action," and strengthening 

 the heart. A stimulant may do the first, but it does 

 not therefore do the second. The reaction following 

 may leave the heart weaker than before. This applies 

 to stimulants generally. 



NATURAL HISTORY JOTTINGS. 

 The Green Tortoise Beetle {Cassida viridis). 



ON August 9th, 1SS1, I for the first time saw the 

 singular larva of the green tortoise beetle 

 (Cassida viridis). It was feeding on the foliage of 

 a thistle that grew on a narrow strip of grass by the 

 wayside. I remarked the canopy of feces, also the 

 fact of the larva eating out the parenchyma of the leaf 

 from one side, and thus forming rounded spaces, 

 which, from the epidermis on the opposite side of 

 the leaf being untouched, gave a spotted or blotched 

 appearance to the food-plant ; in most instances the 

 epidermis was intact over the eaten-out spaces, while 



