SCIENCE.
��The digestion eiperimeiilB offer nothing of special interest in this connection, and we paas at unce to the experiments upon the nutritive value of the digested celialose. These were so arranged as [o compare the effect ol the latter with that of an equal weight of ■ugar ill two respects: 1°, oh to Its influence upon the
Sroteld metabolism of the body; and, 2°, as to ita in- ueDce upon the gain or loss of fat.
The infiuence of carbhydrates in the food, as is well known, is to decrease the proteid metabolism, as ii shown by Ihe diminished excretion of nitrogen in ih: urine. In v, Knierlem's experimenU, 22 grams of crude Qbre, of which 11.02 grams were digested, decreased the proteid metabolism by 22%, while 11 grams of cane-sugar decreased it 15.3%: in other words, the digestible crude fibre showed itself more effective in this respect than an equal weight of sugar.
As regards the gain or loas of fat, the advantage is on the side of the sugar; the latter diminishing the daily loss from the body by 2.5 grams, while the cell- ulose decreased it by 1.7 grams.
These are the results of a single experiment, and, as regards exact numerical values, are of course sub- ject to correction by future in ves ligations. They certainly show, however, that the nutritive value of cellulose is by no means insignificant, and probably not very much below that of other carbhydrates. If. as in Ihe former article, we assume that the heat evolved by the fermentation of the cellulose in the alimentary canal is of use to the organism, then the sole loss by the fermentation Is the latent energy carried off in the marsh-gas evolved. In that paper the amount of that loss was estimated on the basis of Henneberg and Stobmann's determinations of the amount of marsh-gas eicreted in their respiration ex- periments. If, instead of this, the amount of n^arsh- eas evolved in the fermentation of one gram of cellu- lose be made the basis of the calculation, a somewhat tower value for the cellulose results. Acconllng to Tappeiner, one gram of cellulose yields O.SHa grams CO,, 0.O4T grams CH„ and 0.618 grams of organic aeUis. One gram of cellulose yields 4,462 cbI.; 0.04T grams CH,, BHcal.: leaving 3,838 ca I. to represent Uie available heat-value of the cellulose. One gram of cane-sugar yields 4,173 cal.: one gram of starch, 4,479 cal.: consequently, if our fundamental assump- tion is correct, the value of one gram of cellulose is about fi2%of that of cane-sugar, and about ^% of that of starch. These results agree well with those of V. Enieriem's experiments; and the two together appear to justify the conclusion, previously elated, that the nutritive value of cellulose is not greatly inferior to that of other carbhydrates.
H. P. ABM9BY.
The cavjil obBerratory pnbUoatloiis.
Referring to your criticism la Science for April S, on Ihe delay in printing annual volumes of 'Astro- nomical and meteorological observations' made at the 17. S. naval observatory, I am glad to be able to say that the cause for comiilaint in this direction has been, at least temporarily, remiived; and In future we hope to have our volumes printed as fast as the limited number of computers will permit the proof- sheets to be sent to the printer.
During the closing days of congress, the following resolution was Introduced and concurred In: "That the annual vi)lume of the " Aslrononiical and meteoro- logical observations' of the naval observatory for the years 1881 and 1882 be printed, and that 2,000 addi- tional copies of each volume he printed, of which 400
��copies will be for the use of the senate, 800 for the use of the house, and 800 for the use of the navy department, or for sale at the cost of paper and printing."
The manuscript sheets of the volume for ISSl ore now in the hands of the printi^r, lo be followed Im- mediately by those for 1882; so that both of the.te volumes will be distributed this year, and it is hoped that we will continue lo be able to have |as you very pertinently suggest) all annual volumes printed in- dependently of llie regular appropriation fertile navy department, Allan D. Bkows,
Commander, U. S. navy- U. S. nsTnl obacrvilorv, WublngtoD, D.C,
An attempt to photograph the oorona.
Mr. Pickering's interesting experiments described in Srifnce for April 3 would seem to be practically conclusive as to the unreality of the coronal forms which appear upon the plates of Dr. Hugglns and Mr. Woods. If it were evident that he had observed all the conditions which they indicate as es^ential.
Hia letter, however, is silent in respect to one Im- portant point. It is not stated whether or not the plates were ' backed ' with any light-absorbing sub- stance, In order to prevent the so-called ' halation ' produced by reflection from the back surface of the plate under a strong light. The English observers insist urgently upon the necessity of this precaution, and use for tfae purpose, I believe, a t»at of asphalt varnish, colored with Brunswick blautc. Ills possible that even this expedient would not wholly prevent a streaky scattering of light al the edge of the sun's image, because minute particles of foreign matter embedded in the glass itself would have their in- fluence; but It is obvious, that, if the experiment was tried without the precaution, it cannot be looked upon as any way decisive.
Perhaps Hr. Pickering would kindly supplement his (H)mmunicalion by a brief statement regarding this point. C. A. YotTNa.
Prluselon. K.J., April S.
��In reply to Professor Young's communication, I would say that the precaution to which he refers was carefully attended to, and that all the plates employed were hacked the day before the eclipse with asphalt varnish. It would be very interesting to know how far the corona, as photographed by Dr. Ruggins, extends from the sun: lor a very long ex- poBure would probably mask tlifl real phenomenon; one that was very short would be insufficient to obtain an Impression of it. My expo.<>urus were so timed, that, by a long development, the darkening could be traced to a distance of .8 of the sun's diam- eter, while, with a short development, the darkening only reached to .2. But in no case could any par- ticular rays be identlQed in th<> differont photographs. Wm. H. PicEEBmo.
Sir 'William Thomaon'a Sloleonlar dynamics.
As it is possible that «ome ot your reoilers may have obtained copies of the papyrograph report ot my lecture-i on molecular dynamics, delivered at Bal- timore during October, 1884. I should be obliged by your giving publicity to the following corrections: —
P. 84, lines IS and 10, delete ■ We may call It a dynaniax but not a paradox.' I have no recollec- tion of, nor can I Imagine, what the word was that I suggested as more logical tlran * paradox.'
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