494 



BEITISH ASSOCIATION MEETING. 



{Professor Owen's Address,— Contimied from page 450.) 



Last year, M. Poitevin's production of plates of relief for the purpose of 

 engraving by the action of light alone was cited as the latest marvel of photo- 

 graphy. This year has T?itnessed photographic printing in carbon by M. Pretschi. 

 M. Niepce de ISt. Victor has succeeded in reproducing the colour of the original 

 on metallic plates, though he cannot fix it; and these lovely " heliochromes '* 

 unfortunately vanish like the breath from a mirror. Mr. Scaife has obtained a 

 portrait of a shell in full flight a few feet after it left the mortar, with a repre- 

 sentation of phenomena in the development of the smoke too transitory for the 

 eye to ascertain when they occur. Photography may hence superadd a new 

 defining function to the highest attainable telescopic power. 



The first application of the electro-magnetic discovery was, as it should be, 

 to the direct service of the philosopher. The application of a delicate compass- 

 needle would show by its delicate deflection the strength of the voltaic current. 

 Out of this followed the knowledge of thermo-electricity. Faraday's demonstra- 

 tion — the converse of Oersted's — that magnetism could produce electricity, has 

 been succeeded by other brilliant discoveries by that most exemplary investigator 

 of natural laws. Out of Oersted's painfully-pursued experiments with his little 

 magnets, voltaic pile, and bits of copper-wire has come the electric telegraph I 



Eacon, commenting on the " History of the works of Nature," describes it as a 

 chaos of " fables, antiquities, quotations, frivolous disputes, philology, ornaments, 

 and table-talk." Since his day, the chief steps by which natural history has 

 advanced to the dignity of a science are associated with the names of Ray, 

 Linnaeus, Jussieu, Buflbn, and Cuvier. Now, not only has the structure of the 

 animal been investigated even to the minute characteristics of each tissue, but 

 the mode of formation of such constituents of organs, and of the organs themselves, 

 has been pursued from the germ, bud, or egg, onward to maturity and decay. To 

 the observation of outward characters is now added that of inward organization 

 and developmental change, and zootomy, histology, and embryology combine their 

 results in forming an adequate and lasting basis for the higher axioms and 

 generalizations of zoology properly so-called. 



The study of homologous parts in a single system of organs — the bones — has 

 mainly led to the recognition of the plan or archetype of the highest primary 

 group of animals, the vertebrata. The next step of importance will be to deter- 

 mine the homologous parts of the nervous system, of the muscular system, of the 

 respiratory and vascular systems, and of the digestive, secretory, and generative 

 organs in the same primary group or province. It is of more importance to settle 

 the homologous of the parts of a group of animals than to speculate on such rela- 

 tions of parts in animals constructed on demonstratively distinct plans of organi- 

 zation. What has been effected and recommended in regard to homologous parts 

 in the Vertebrata should be followed out in the Artimlata and MoUusca : — ■ 



" The present state of homology in regard to the Articulata has sufficed to 

 demonstrate that the segment of the crust is not a hollow expanded homologue of 

 the segment of the endoskeleton of a vertebrate. There is as little homology 

 between the parts and appendages of the segments of the vertebrate and articu- 

 late skeletons respectively. The parts called mandibles, maxillss, arms, legs, 

 wings, fins, in insects and crustaceans, are only 'analogous' to the parts so called 

 in Vertebrates ; and to express definitely the clear ideas now possessed of their 

 essential distinction, will require a distinct nomenclature." 



The investigations of the vitellus, of the entozoa, of the metamorphoses of insects, 

 and the subjects investigated by means of the microscope, are next passed under 

 review. 



^ A very interesting application of the microscope to the examination of the par- 

 ticles of matter suspended in the atmosphere has been made. Cloudy extents of 

 dust-like matter pervading the atmosphere, which have been variously observed, 

 have been thus found to consist of the pollen of plants, vegetable species, and 

 DiatomaceaD, and this investigation promises to be productive of other important 

 results. 



