May 13, 1880] 



NA TURE 



31 



markings of Sigillaria:, longitudinal flutings and the usual leaf- 

 scars, stigmarian roots and rootlets attached, &c., others not so 

 well preserved, being of doubtful affinities. Of course they are 

 now but casts, nothing remaining of the original trees except a 

 thin film of coaly matter representing the bark. They measure 

 in height from three to ten feet, and have a diameter of from 

 one foot to two feet four inches. I think it may be safely stated 

 that they were merely hollow stumps when finally submerged, 

 fronds of ferns, lepidodendroid twigs and leaves, and other 

 vegetable waifs having found their way info the hollow cylinders 

 and left their impress on the inclosed matrix. 



I may add that there are several horizons of growth, one 

 forest having grown above another ; stigmarian roots and root- 

 lets, calamites, lepidodendroid stems and leaves, lepidostrobi, 

 and masses of leaves of unascertained species being indiscrimi- 

 nately mixed throughout the whole section, the ferns, however, 

 being met with in greatest numbers near the bases of the erect 

 trees. 



It is perhaps worthy of remark, too, that there is no accumu 

 lation of coaly matter in the section revealed, nor is there any of 

 the usual " floor clay " about the roots of the trees. 



29, Radcliffe Street, Oldham JAS. Nield 



Fungus Inoculation for Insects 



The importance attributed by Dr. Lankester (Nature, vol. 

 xxi. p. 448) to " Prof. Metschnikoff's suggestion of a deliberate 

 cultivation of an insect's-disease-producing fungus, and the 

 application of the cultivated fungus in quantity to places in- 

 fested by these insects," invites attention to the fact that the 

 suggestion has been anticipated in a very serious and earnest 

 way by my friend the distinguished entomologist. Dr. John L. 

 I-e Conte of Philadelphia, in his presidential address before 

 the Portland metting of the American Association for the 

 Advancement of Science, in August, 1873. 



His address concluded with ten suggestions for the promotion 

 of economic entomology in the United States, and the seventh 

 reads thus: — "Careful ;tudy of epidemic diseases of insects, 

 especially those of a fungoid nature ; and experiments on the 

 most effective means of introducing and communicating such 

 diseases at pleasm-e." 



The reasons for making this suggestion are fully stated in the 

 preceding paragraphs of the address, where the observations on 

 which it is based are detailed. 



Dr. Le Conte's first suggestion was, " Reorganisation of the 

 Department of Agricnltui'e [at Washington] on a scientific basis, 

 for the proper protection and advancement of agricultural in- 

 terests." Had this suggeslion received the attention which has 

 been given to many other subjects of less practical importance, 

 the present reclamation for him of priority in the case of his 

 seventh suggestion, would probably have been rendered un- 

 necessary ; and the credit of introducing a more reasonable 

 method of extirpating insect-pests than the dangerous plan of 

 distributing potent mineral poisons to careless or uneducated 

 persons for use in the fields, would have been secured to the 

 nation to which we have the honour to belong. 



Dr. Le Conte's address may be found in the published vulume 

 of the Proceedings of the Portland meeting ; but it was reprinted 

 by him and extensively circulated and favourably commented 

 upon at the time, his desire being precisely that so well ex- 

 pressed by Dr. Lankester "to do something to persuade 'prac- 

 tical ' men that all science is deserving of their respect and 

 encouragement." We all hoped that such earnest words from 

 so high an authority would have their due effect upon Congress 

 and inaugurate a long-desired reform of our Agricultural Bureau. 

 But it has happened, as in sd many other instances, that we 

 have had to wait seven years before even an echo reaches us 

 from a distant part of the world, where the labours of Prof. 

 Metschnikoff have procured an intelligent appreciation of the 

 value of Dr. Le Crnte's suggestion, so little comprehended by 

 the powers at home. - J. P. Lesley 



1,008, Clinton Street, Philadelphia, April 10 



Carnivorous Wasps 

 A SERIES of letters, under the' above heading. Lave appeared 

 in Nature for several weeks past. The facts they contain, 

 although interesting in themselves, are nothing new to ento- 

 mologists. That wasps are carnivorous, that they chae flies, 



&c., was known long ago (compare Westwood's "Introd. to 

 Entomol.," ii. p. 246). That wasps cut off the wings of flies 

 before sucking them was observed by Dr. Erasmus Darwin 

 in the last century (see J. H. Fabre, "Souvenirs Entomolo- 

 giques," Paris, 1S79). An Old Entomologist 



Heidelberg, Germany, May 6 



Seeing by Telegraphy 



We beg to thank Mr. Gordon for drawing attention to the 

 fact that the principle of rotation of plane of polarisation of light 

 in a magnetic field could not actually be employed with the form 

 of receiver symbolically described by us in Nature, vol. xxi. 

 p. 5S9. Having satisfied ourselves that there could be no doubt 

 of the feasibility of using the first form of apparatus, which we 

 spoke of, as a receiver in a sight telegraph, we merely wished to 

 point out, at the end of our letter, that otlre.r methods might 

 perhaps be employed ; and we still have no doubt that with a 

 certain proper arrangement of the apparatus not only the effects 

 observed by Dr. Kerr, but other of the Faraday polarisation of 

 light effects might be practically made use of. For it must be 

 remembered that the actual electric currents now used to transmit 

 articulate speech are only one forty-millionth per cent, as strong 

 as those necessary to work even a delicate telegraph relay, 

 whereas it required several Grove's cells to show in a decided 

 way the old experiment of the sound emitted by an iron bar on 

 being magnetised. 



And in fact we may go further, and mention that we have for 

 the last year, or more, held the view that just as all electric con- 

 ductors turn into heat energy a portion of the energy they transmit 

 as electric current, so there must be some bodies, presumably of 

 the sulphur selenium order, which, when properly employed, will 

 convert a portion of tte current energy into vi-ible_ lumirious 

 vibratior.s, and may therefore be used as receivers in a iight 

 telegraph. 



As to the other objection that mii^-ht have been made to the 

 method as popularly described by us in consequence of the large 

 number of wires, we need hardly mention that in practice a 

 telegraph engineer would avail himself of the principles of 

 multiple telegraphy. John Perky 



May 3 W. E. Ayrton 



Anchor-Ice 



In confirmation of Mr. Rae's views upon this subject, the 

 following results of observations made upon the Charles River, 

 Mass., may be of interest. 



Anchor-ice is usually formed at night during a sudden "cold 

 snap," when the river is not covered with surface-ice. It seems 

 to consist of sma'l masses of needle-like crystals grouped in 

 stellate forms, and distributed pretty evenly throughout the body 

 of water. 



These adhere readily to any obstruction, and accumulate 

 rapidly upon it. Thus the racks or strainers through which the 

 water passes to the mills are covered and closed by it, so that 

 the flow of the water is absolutely stopped, and the mills can 

 only be kept running by constantly removing it with a rake. 



It is very adhesive and tenacious. I have frequently seen it 

 accumulate upon portions of the extreme edge of a mill dam 

 (over w hich was pouring water a foot in depth) until it reached 

 the surface, re-isting for a considerable time the enormous 

 pressure to which it was thus subjected. It usually disappears 

 soon after sunrise. 



Detached portions of the accumulated masses always rise to 

 the surface, but the original crystals, if not heavier than water, 

 seem to be at least as heavy. The general appearance of this 

 ice when removed from the water resembles that of sherbet or 

 "water ices." As these are frozen quickly while in motion, 

 they are apparently formed under similar conditions. I have 

 never seen anchor-ice except in rapid currents. n -a n 



Boston, U.S.A., April 24 C. F. C. 



SoDic Chloride Crystals.— Dr. Ord refers Dr. Ralton to 

 Dr. Scale's book on "Kidney Diseases, Urinary Deposits, &c., 

 ed. 1869, p. 167, and the figure at p. 130; also Thudichums 

 " Pathology of the Urine." 



Oxoniensis.— Apply to the Secretary, Brhish Association, 

 Albemarle Street, W. 



