128 



NA TURE 



[October 14, 1922 



this first trip could give, you may take more stations 

 and investigate smaller areas more carefully. 



I am glad to be able to say that in 1921 Dr. Russell, 

 on the English steamer John Bligh, made the first 

 trip across the North Sea with my bottom-sampler, 

 guided by my assistant, Dr. H. Blegvad ; they found 

 some of the same communities between Lowestoft 

 and Esbjerg as we know from the Kattegat. 



Thanks to the bottom-sampler we can now speak 

 about areas with a Venus mussel community, an 

 Amphiura filiform: s community, a Brissopsis Am- 

 ■■!•: chiajei community, and so on, as we on land 

 speak about a heath, a beech-wood, a meadow, etc. ; 

 we are also able to get a quantitative idea of the 

 amount of animals on the sea-bottom, and are able 

 to follow seasonal or other variations therein. 



A dredge will sometimes give us, when well used, 

 a bagful of animals, belonging to the epi-fauna as 

 well as to the ordinary communities, and taken up 

 from all the communities it has been towed over. 

 The dredge is inclined, moreover, to take all animals 

 on, not in, the bottom, and its content is therefore 

 not a true illustration of what is living 111 or on the 

 bottom, but a mixture mostly of epi-fauna from 

 different communities, without giving the slightest idea 

 of quantity per square metre. The content of a dredge 

 and .1 bottom-sampler used on the same station will 

 very often give quite different collections of animals. 



The dredge has given excellent information to 

 zoologists wishing to collect rare animals for preserva- 

 tion in alcohol, and for dredging oysters, and so on, 

 but a true illustration of the fauna on the sea bottom 

 it never has given and never will give. 



I admit one thing : it is easy for me to speak and 

 write about the bottom-sampler work, but it never 

 will be well understood without seeing the work going 

 on on board ship ; many men of science from Europe 

 have seen how quickly the sampler may be used, 

 like an ordinary sounding machine, and how well it 

 works. I should be glad to welcome many more 

 visitors at the Danish Biological Station, not only 

 to see the bottom-sampler working, but also to be 

 able to discuss with them the problems which have 

 arisen in my mind while using this method during 

 the last 10 to 12 years. 



It was a Dane, O. Fr. Muller, who first introduced 



the dredge in northern Europe for scientific use, and 

 it will always be used by zoologists and for special 

 purposes, but only the bottom-sampler is able to give 

 a true and quantitative representative illustration of 

 the bottom fauna. 



Finally, I wish to say that to have a bottom- 

 sampler and to use it is not enough to become a 

 great marine biologist ; it depends much upon the 

 possession of working ideas. The bottom-sampler is 

 not able to solve every question ; it cannot, e.g., take 

 animals living very deep in a hard bottom, and the 

 apparatus must be modified for special work, accord- 

 ing to the size of the ship used, the depth at which 

 you are working, etc., and it is necessary to supple- 

 ment the investigation by means of other apparatus, 

 fishing-gear, dredges, etc. But without quantitative 

 work it is not possible to understand the principal 

 features of the fauna of the sea-bottom. 



It would be a matter of great scientific interest to 

 have a bottom-sampler used down the slope of the 

 continent at all depths, out on the very ocean floor, 

 to determine all the communities living here, and to 

 prove how barren the ocean floor really is. It would 

 also be of great interest to follow our European 

 communities from the North Pole down to Cape 

 Town, to study their geographical distribution, to 

 determine the perfectly unknown Arctic communities, 

 and the unknown tropical communities. I have 

 given a hypothetical chart in my Report No. 22, but 

 it has to be verified. I am too old to do that, and 

 my steamer too small. I hope other men will do it. 

 1 ,1111 sure the geologists would be glad to know 

 something about these communities, based upon the 

 common animals. I am certain that, like me. they 

 care much more for common characteristic species 

 and their distribution than for " rare " animals. 



The productivity of the bottom fauna in European 

 waters is by no means unlimited ; it is, therefore, a 

 matter of the greatest importance for some of the 

 greatest fishery questions to know as much as possible 

 about this productivity. The English fishermen arc, 

 as I often have heard, the backbone of the English 

 navy ; they depend upon the fishes, and these in turn 

 depend upon the fish-food. Careful investigation of 

 the latter is, therefore, a matter of great importance — 

 particularly for Great Britain. 



Adhesives. 



Bv Emil Hatschek. 



'THE treatise of Theophilus Presbyter, entitled 

 -*• " Diversarum Artium Schedula," and well 

 known to all students of the history of painting, gives 

 directions for the preparation and use of glues from 

 leather and deers' antlers, of plum- and cherry-gums, 

 and of mixtures of cheese and lime described as 

 " cheese glues." This list of adhesives familiar to 

 craftsmen at the end of the eleventh century covers 

 practically all the types in use at the beginning of the 

 twentieth century. A similar degree of old empirical 

 perfection is shown by many arts employing colloidal 

 material, and the student of colloid chemistry anxious 

 to magnify his office is perpetually confronted with 

 the task of explaining the rationale of traditional 

 procedure and of suggesting improvements based on 

 theoretical grounds. 



The difficulties of this task are well illustrated by 

 the first report of the Adhesives Research Committee. 1 

 I owards the end of the war a shortage of glue and of 

 the chief substitute, casein, threatened to limit the 

 output of aircraft, and the labours of the committee 



NO. 2763, VOL, I IO] 



were accordingly directed, on one hand, to a close 

 study of glue, and, on the other, to the discovery of 

 possible substitutes other than casein. The report 

 contains much interesting and novel matter under 

 both heads. 



The difficulties in the way of a rational study of 

 glue seem to be twofold. The first is that the only 

 criterion of its value as adhesive is a mechanical test 

 of a glued joint between wooden test pieces of specified 

 nature and size. The report describes the conditions 

 (■t siu h a test, as finally adopted, and sets forth the 

 possible sources of error. Both on theoretical and 

 on practical grounds (about five days have to elapse 

 from the soaking of the glue to' the actual breaking 

 test), it is desirable to find some easily measured 

 constant which shows a simple quantitative relation 

 with the breaking strength. No such constant is 

 yet known, although empirically the setting time of 

 the glue sol, the melting point of the gel and its 

 " strength," i.e. roughly speaking, its modulus of 

 elasticity, furnish some indication of its quality. 



The second difficulty is of a more fundamental 

 nature. It is known that pure gelatin is not a good 



