July, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



flesh should be quite free from objection. It is, therefore, 

 of special interest at the present time to see what risks are 

 run in eating such meat. It is asserted that the flesh of 

 animals suffering from tuberculosis and other diseases is 

 frequently used in these preparations. Although in the 

 case of tuberculosis the practice is very objectionable, there 

 would seem to be little risk of the flesh of an uninfected 

 part of the animal conveying the disease to man, and even 

 when the disease was general thorough cooking would 

 destroy the bacilli and probably the toxic substances pro- 

 duced by them. There is, however, much more danger in 

 eating the flesh of animals infected with the various bacteria 

 that produce septicaemia, since their toxic products are only 

 partially destroyed by heat. The flesh of animals suffering 

 from anthrax, malignant cedema, and chicken pox is also 

 dangerous whether in the raw or cooked condition. But 

 this danger is one to which the consumer of fresh meat is 

 also liable, whenever the system of inspection is defective. 

 A greater danger in tinned meats than the presence of 

 disease organisms and their products is that flesh contain- 

 ing putrefactive products may have been used. Wholesale 

 putrefaction of the contents of the tin would, of course, 

 make itself known when the tin was opened, but this would 

 not be the case if flesh in a state of incipient decomposition 

 had been used, for the sterilising process would have 

 arrested any further change. The meat in the tin might, 

 in fact, be absolutely free from bacteria, and yet be poison- 

 ous. The products formed by the bacteria are even more 

 dangerous than the organisms themselves. Thus, in Ger- 

 many, there have been wide-spread epidemics of what is 

 known as butulism, a severe form of poisoning through 

 eating raw or imperfectly cooked sausages. These have 

 been found to be due to a definite toxine produced by 

 Bacillus botuliiLus in flesh from which air is partially ex- 

 cluded. This toxine has also been found in poisonous hams, 

 but as it is destroyed by heat it is not likely to occur in 

 tinned meat that has been properly sterilised. But there are 

 numerous other bacterial products — the ptomaines — which, 

 unlike true toxines, are not destroyed by heat, and it is to 

 one or more of these that most of the not very frequent 

 cases of poisoning by tinned meat can be attributed. Many 

 of them are simple substituted ammonias, such as 

 putrescine, C12H12N2, while others contain oxygen. 

 Cadaverine, neuridine, and saprine are diamines, allied to 

 pidresciiie, and, like it, are only slightly poisonous, but 

 ■inrlli ijl-iiu<iiiiiline, C2H7N3, which has been isolated from 

 drr(.ni|n.siii- horse flesh and beef, is extremely toxic, and 

 wliin iiijiili-tl into a small animal causes death within 20 

 minutes. Neurine, C5H13NO3, a ptomaine formed on the 

 fifth or sixth day of putrefaction, is also very poisonous, 

 while muscarine, C5H15NO3, from decomposed fish, is still 

 more deadly. It appears to be largely a matter of time 

 whether or no a particular ptomaine is produced among the 

 continually changing products formed by putref.-ictive 

 bacteria, and hence if there be truth in the report of unclean 

 conditions in the factories it is by no means unlikely that 

 particles of very dangerous flesh may become mixed with 

 the fresh meat in the canning process. This may be re- 

 garded as the chief danger of tinned meat, and the only 

 means of guarding against it is a thorough and systematic 

 inspection of the factories, so as to insure absolute cleanli- 

 ness. 



GEOLOGICAL. 



By Edwaku a. Martin, F.G.S. 



About Dew-Ponds. 



In reviewing a book in tlic May number of " Know- 

 ledge " on neolithic dew-ponds and cattle-tracks, I referred 

 to the statement made by Dr. Hubbard that there was a 

 wandering band of men who were going about England, in 

 whom was vested the secret of making these ponds. The 

 object they aimed at was to cause an artificial precipitation 

 of dew by a combination of thatch and puddle. It would 

 be interesting to know more of the people who are said to 

 be occupied in this pursuit. .Vt a paper re.ul at the meeting 

 of the S.E. Union of Scientific Societies at Eastbourne last 



month, Mr. Jenner referred to these ponds, and also to a 

 builder at Alfriston who was stated to be engaged in making 

 them. In visiting this maker of ponds I found that all 

 that he had made had merely received a foundation of con- 

 crete, whether they were situated on high or on low ground. 

 .A dew-pond is a definite kind of pond, and must be re- 

 garded as quite apart from those which are merely made 

 with an impervious bottom, and depend on rain and run- 

 nels for their supply. It is obvious that a pond situated 

 on the top of a chalk down may receive a slight addition to 

 its sum from the rainfall upon its surface, but natural 

 runnels to feed it would be impossible upon so pervious a 

 soil. .Such would not be entitled to be called dew-ponds, 

 unless it were known that the supply was attributable to 

 an artificially-induced precipitation of dew. 



Ponds on Worms Heath. 



In " Neolithic Man in North-East Surrey," by W. John- 

 son and W. Wright, a cheaper re-issue of which we are glad 

 to welcome, mention is made of a dew-pond on Worms 

 Heath, and the suggestion is made that by puddling the 

 bottom, a pond was formed in the depression of a neolithic 

 hut-circle. I am not sure from the context that one can be 

 quite satisfied that this is a true dew-pond, since with the 

 removal of the shingle the clay bottom has, in some of the 

 gravel pits on Worms Heath, resulted in a good deal of 

 water lying stagnant there, and this pond may, perhaps, 

 have formed spontaneously. On page 47 of the same book 

 the authors refer to the strange sight seen in some parts of 

 carts being sent up hill to obtain water from dew-ponds, or 

 mist-ponds as they have often been called. It may, per- 

 haps, be suggested that the immortal Jack and Jill obtained 

 their supply from a dew-pond, since they were compelled to 

 go " up the hill." Gilbert White makes some interesting 

 remarks concerning one which was situated on Selborne 

 Down, 300 feet above his house. It was never above 3 feet 

 deep in the middle, nor more than 30 feet in diameter, yet it 

 was never known to fail, though it afforded " drink for 

 three or four hundred sheep, and at least twenty head of 

 cattle beside." Unfortunately this pond when last I visited 

 Selborne had at length become dr\ . 



The Connection of Volcanic Action with 

 Ii^arthquakes. 



In considering the many earthquakes shocks, small and 

 large, which are constantly adding their quota to the 

 tremiflous condition of the globe, one cannot but be struck 

 by the ignorance in which we still remain as to the con- 

 stitution of the earth's interior wdience such shocks 

 originate. Certain lines of weakness, as they are called, 

 present themselves on the surface, and these are marked by 

 active volcanoes, and for the most part they appear in those 

 parts where, so far as we can judge, the crust has been 

 weakened by denudation, or where the fall is very rapid 

 from a great height to a great depth, as on the Pacific 

 slojje of America. Earth tremors are closely connected with 

 invisible intrusive volcanic action, and this results from con- 

 traction brought about by the cooling of the globe. It is 

 not easy to imagine volcanic action without shocks, but on 

 the other hand shocks may be felt, the connection of which 

 with volcanic action is not so apparent. 



Whence the Lava may be Derived. 



Eor the supply of erupiioiis .Mr. O. Eisher imagined a 

 liquid zone at a depth of about 30 miles, although its depth 

 would not be constant. A chilling at the surface due to 

 removal of material by denudation would result "in a de- 

 pression of the boundary limit, whilst on the other hand, a 

 deposition of some thousands of feet of sediment would 

 cause it to be raised nearer to the surface. By this means 

 we should have what has been called the " melting off of 

 the roots of mountains," and this would, in a w-ay, account 

 for the sniallness of the deviation of the plumb line when 

 tested with a mountain mass. When, too, one sees the 

 enormous foldings and contortions of palaeozoic and arch<can 

 rocks, one may well ask how such foldings would be possi- 

 ble, unless the strata were in touch with some fluid mass 

 yielding to the superincumbent mass and its movements. 

 Some of the overthrusts, of enormous extent, w-ith which 

 we arc familiar in pre-Cambrian rocks, almost baflle one if 

 one is to consider them as having taken place while the 

 rock was as solid as we now see it. Grant for a moment 



