Sept. lo, 1 8 74 J 



NATURE 



381 



Photographic Irradiation 



In Nature, vol. x. p. 245, Mr. \V. C. Crofts adds his experi- 

 ence to those previously given in your journal, and gives his 

 conclusion as opposed to that of Mr. Aitken (vol. x. 

 p. 185). Like most conclusions based on incomplete evi- 

 dence, it does not conclude anything. The fact is as I 

 have stated it in my previous note (vol. x. p. 205) on 

 the subject, and when I return to England I will be most happy 

 to demonstrate it to anyone who cares lo e.xamine the question 

 thoroughly. Mr. Crofts' experience with the Liverpool dry 

 plates agrees with my own, for these plates are prepared with a 

 pyroxyline which gives a minimum of irradiation when " backed," 

 and give the best quality of image for scientific purposes attain- 

 able with a bromide film ; but certain qualities of pyroxyline 

 prepared in precisely the same way will show irradiation that 

 nothing can cure, even when used for makmg transparencies by 

 contact, where, of course, there can be no question of influence 

 of any optical delects. The unquestionable fact that a collodio- 

 albumen film acts in so totally different a manner from one of 

 bromized collodion should prove that the lens has next to nothing 

 to do with it. 



My conclusions may be very imperfect, but so far as they go 

 they are definite, and are drawn, not from two or three, but 

 from hundreds of experiments with all kinds of dry plates and 

 many dilTerent samples of pyroxyline, and whatever tliey may be 

 Worth, they fully support Mr. Aitken's views. 



New York, Aug. ig W. J. Stillman. 



Pfluger on the " Salivary Glands " of the Cockroach 

 I \v.\s much interested in reading Prof Redfern's able address 

 at the British Association this year, more especially with that 

 poition which dealt with the oDservations of Prof. Pfliiger on the 

 histology of the so-called " salivary glands " of the cockroach. 

 In the year 1871 I wrote a short paper in Professors Humphry 

 and Turner's Journal (vol. v. p. 242 et scij.) upon these 

 organs. In this I ventured to doubt the truth of tke generally 

 accepted hypoihesis as to their lunctions. My reasons for so 

 doing may be summarised as follows : — i. The appendages in 

 question are perforated throughout by ramifying spirally coated 

 tubules difiermg only from trachea; in this respect ; during their 

 passage through the organs in question they receive a layer ex- 

 ternally of yellowish tissue, which may be, as Prof. Pfliiger 

 suggests, epiihelial glandular tissue. 2. These tubules with the 

 sacculi opening into them can be more or less fully injected with 

 a liquid by simply immersing the insect in a suitable menstruum, 

 and placing it under the exhausting receiver of an air-pump. 

 This experiment demonstrates indubitably that this tubular system 

 contains an clastic Jhdd, which for anatomical. and other reasons 

 I conclude to be air. 3. As far as my experience carried me, 

 the sacculi, the supposed reservoirs of the saliva, never contained 

 naturally any liquid whatever, Imt upon opening the thorax were 

 invariably found to be collapsed and apparently empty. This is 

 precisely what would occur supposing that during life they were 

 filled by and communicated readily with the external air. 



I have not yet had an opportunity of referring to Prof. Piliiger's 

 paper, and I am consequently obliged to accept his statements 

 at second hand. In noticing the intimate connection there is 

 between these organs and the nervous system of the insect, he 

 confirms what 1 have myself observed. It is some years since I 

 last anatomised a cockroach, and meanwhile I suppose these 

 insects have utilised their organs in the w.ay mentioned by Prof. 

 PAugei", and we can now see " transparent drops . , . transuding 

 from the ends of cells when the saliva has been made to flow by 

 irritation of the gland." On looking over my microscopic speci- 

 mens I find that I still have by me one showing the so-called 

 ** salivary duct " and a sacculus injected in -the way I liave men- 

 tioned. Any one may satis'y himself that this result is 

 feasible by trying the experiment. In doing so the only caution 

 required is to e.\haust the air gradually and lo keep the immersed 

 insect in a partial vacuum for a few hours. Failure under these 

 circumstances is almost impossible. 



London, Sept. 2 AV. AiNSME HoLLi.s 



THE CONFERENCE FOR MARITIME 



METEOROLOGY 



THE Conference, held at the Meteorological Office, 

 116, \'ictoria Street, for the purpose of reconsider- 

 ing the decisions regarding maritime meteorology made 



at the Brussels Conference in 1853, has concluded its 

 sittings, and the Report of its proceedings will be pre- 

 sented to the Permanent Committee, app Dinted by the 

 Meteorological Congress of Vienna (of 1873), which holds 

 its meeting at Utrecht in the course of the present week. 

 The Conference consisted of twenty-five members, be- 

 longing respectively to every maritime country of con- 

 sequence in Europe, except Sweden and Turkey. India 

 and China were also represented. Prof. Buys Ballot was 

 elected president, and Capt. Hoffmeyer and Mr. Scott, 

 F.R.S., secretaries. It met on the 31st ult., and at once 

 subdivided itself into two sub-committees, dealing with 

 the various questions connected with (i) " Observations," 

 and (2) " Discussions." Each sub-committee held four 

 sittings, and at the closing meeting of the Conference the 

 several resolutions framed by the sub-committees were 

 adopted, in most cases unanimously. Inasmuch as the 

 Conference was an outcome of the Vienna Congress, these 

 resolutions will not be published utitil they have been 

 communicated to the Permanent Cominittee as above 

 mentioned. Their general scope is towards the attain- 

 ment of greater uniformity in the methods of meteor- 

 ological observation at se.i, and of subsequent publication 

 of the results. On Thursday, by kind permission of the 

 Astronomer- Royal, the members went to Greenwich in 

 the morning, where they were conducted over the mag- 

 netical and meteorological department by Mr. J. Glaisher, 

 F.R.S. In the afternoon they spent some hours at Kew 

 Observatory, where they were received by Mr. Jeffery, the 

 superintendent, and in the evening the whole party was 

 entertained at dinner at the Star and Garter, by some of 

 the members of the Meteorological Committee. On Fri- 

 day several members availed themselves of the great 

 courtesy of the War Office, and repaired to Woolwich, 

 where they were conducted over the Arsenal by Colonel 

 Field and other officers connected with that department. 

 Finally, on Saturday, they inspected the .Meteorological 

 Office, where the meetings of the Conference had been 

 held, and paid special attention to the arrangements there 

 existing for reproducing the records of the photographic 

 and other instruments at the several observatories in the 

 United Kingdom. 



ON SEWAGE AND SEWAGE FARMING 



No. I. — Northampton. 



A FTER having had practical experience of the fer- 

 -^'*- tilising effects of sewage and liquid manure, I have 

 for several years devoted part of my leisure time to an 

 examination of the arrangements adopted by the principal 

 cities and towns for disposing of sewage. At first I looked 

 at it from the agricultural stand-point ; but as I proceeded 

 with the inquiry I had to widen the range of view. 



The place I \isited last is Northampton. I propose 

 at present to write a concise note of what the authorities 

 of thst town have done. 



Northampton has a Board of Commissioners for deal'n"- 

 with sewage and kindted nuisances, which is distinct froni 

 the corporation. I believe their number is limited to 

 twelve ; of whom six belong to one political body, and six 

 to the other. These twelve Commissioners, as a body, 

 must, therefore, be non-political ; six of one being equal 

 to half-a-dozen of another. 



The town contains at present about 50,000 people. 

 Many experiments were made at the expense of this body 

 for purilying the fewage. At last they adopted the 

 scheme which I proceed to describe. 



Near the town there is a number of tanks in which the 

 sewage is allowed to settle for some time so as to enable 

 the more bulky of its solid contents to fall to the bottom 

 and be collected. Deprived of these solid matters, 

 the sewage is conveyed in a main culvert, about four miles 

 froin the town, where it is received on a tract of ground 



