io8 



HARDWICKE'S SCIENCE-GOSSIP. 



nature-printed pictures of all that such telescopes can 

 reveal ; and those who agree with me in the conviction, 

 that the diffusion of scientific knowledge and scientific 

 taste is of even more importance than mere scientific 

 discovery (discoveries communicated only to a few 

 are but little better than vaporous material for the 

 inflation of pedants), will welcome very heartily this 

 great step in celestial photography. The vexed 

 question of whether any volcanic action capable of 

 producing visible changes on the surface of the moon 

 is still proceeding will probably be settled, or at any 

 rate be more approximately answered than by the 

 method of comparing the drawings of one observer 

 with those of another of different date. 



The Photographic Pictures by Charles 

 Breese. — Instantaneous photography, which is gene- 

 rally supposed to be a very recent invention, was 

 successfully achieved by the late Charles Breese quite 

 thirty years ago. He kept his process secret, and the 

 secret died with him. I purchased all that remained 

 of his stereograms after his death, and still have 

 many duplicates. They remain unrivalled, especially 

 the sea-pieces, where breaking waves and fine atmo- 

 spheric effects are displayed. A picture of the moon 

 about an eighth of an inch in diameter was the subject 

 of much discussion at the time of its publication. 

 Learned members of the Photographic Society proved, 

 mathematically of course, that the actinic energy of 

 the lunar rays could not possibly produce such a 

 picture, which, taken thus by a common camera in 

 fixed position, must be instantaneous, seeing that 

 otherwise the change of position due to the earth's 

 rotation would produce an elongated instead of a 

 circular figure. It was therefore described as a 

 "painted moon." To refute this calumny I threw 

 the image on a screen by means of a lime-light 

 lantern, which displayed details that could not have 

 been painted as asserted ; but I soon found a limit to 

 this method of magnifying ; the collodion film dis- 

 played a picture of its own special details more 

 prominently than those of the lunar landscape — a net- 

 work of cracks otherwise invisible. I have not yet 

 learned whether the modern gelatine film is similarly 

 defective. The possibilities of carrying forward the 

 work described above will largely depend upon this. 



Mrs. Ogilvie, of Sizewell House, Suffolk, has 

 just presented the Ipswich Museum with a cheque for 

 1300/. to defray the debt on the new buildings, in 

 token of her admiration of the good work being done 

 by Dr. J. E. Taylor, the Curator, in the elevation 

 and education of the people by means of his popular 

 lectures. 



M. Faye, the French geologist, thinks that the 

 earth's crust must be thicker and denser under oceans 

 than beneath continents, because the earth's heat has 

 always radiated more freely there. 



CHAPTERS ON ANIMAL PARASITES. . 

 By W. A. Hyslop. 

 No. I. 



THE subject of animal parasites is looked upon by 

 many as one of loathing, and not to be talked of 

 or discussed in polite society ; and this arises more 

 from want of knowledge than anything else, as there 

 is as little reason to avoid the mention of the word 

 "parasite" as of any other word in science. The 

 study of parasites opens the mind in a large degree, 

 and the more intimate one's knowledge the less does 

 he loathe, and the more does he admire, the wonderful 

 provision made for these beings in the domain of 

 Nature. That all parasites are hurtful is one of the 

 numerous popular errors on the subject. Some most 

 certainly are injurious when in large numbers, but by 

 far the larger number are not hurtful ; and indeed 

 some naturalists have, not without good reason, con- 

 sidered them beneficial, as they act the part 0$ 

 scavengers, removing the epidermis, etc., from their 

 hosts. 



Fig. 72. — Ornithymia of Pigeon 

 (slightly mag.). 



Fig. 73. — Lipoptena of 

 Stag (slightly mag.). 



The word " parasite " means literally eating beside^ 

 or at the table of another, and parasites have been 

 loosely defined as "those whose living depends on 

 other living creatures." This definition is rather 

 wide, and might with advantage be limited to " those 

 whose living depends on, and whose habitat is, other 

 living creatures." If this definition be adopted, you. 

 throw out of the category of parasites all such insects, 

 as mosquitoes and midges, which only attach them- 

 selves to human beings and animals momentarily, and 

 then fly off, and do not have, like true parasites, their 

 abode on their hosts. Professor van Beneden has 

 divided parasites into three divisions : the first he 

 terms Commensaux, or Messmates, and includes 

 those which for their living do not depend on theii 

 hosts, but merely profit by remaining at their tables ; 

 secondly, Mutualists, which live exclusively on the 

 natural excretions of animals ; and, lastly, Parasites 

 proper : that is, those which for their livelihood 

 require the blood of their hosts. M. Megnin, again, 

 divides the subject into two main divisions, viz. those 

 which are hurtful, and those which are not. For our 

 present purpose it will probably be more simple, 

 without entering into a discussion as to what place 

 in the animal kingdom the Anoplura, or lice, and 



