July 15, 1880] 



NATURE 



241 



consisted of a cannon-ball weighing about 5 lbs., suspended by a 

 fine ^teel wire, which at its upper end passed through a hole drilled 

 in an iron plug. The pendulum would continue to vibrate for 

 si.xteen or eighteen hours after being set in motion. After 

 obtaining satisfactory results by using a ring of sand in the 

 ordinary manner, a very stiff bristle was attached to the terminal 

 spindle, and under it was placed a thin smoked-glass plate. 

 The resistance was too great to allow the bristle to strike 

 against the plate at each vibration of the pendulum, so that the 

 device was adopted of fixing the plate upon a heavy brass disk 

 capable of being raised or lowered by levelling-screws. This 

 was placed under the pendulum before the latter was set in 

 vibration, and then carefully raised until the bristle scratched its 

 trace on the smoked-glass plate. After two or tlu-ee oscillations 

 of the pendulum the plate was lowered, great care of course 

 being taken to avoid all possibility of rotation during this opera- 

 tion. At the expiration of fifteen, thirty, or sixty minutes it 

 was again raised, and this process was repeated as often as 

 desired. The inclination of the tracings was beautifully shown, 

 and its amount agreed exceedingly well with that given by 

 theory. With a heavier ball and longer wire even better results 

 might have been obtained, but the motion of the pendulum used 

 was but very slightly interfered with by the friction of the 

 bristle. I should not omit to mention that the details of the 

 experiment were carried out by Mr. F. W. Very, then a student 

 at the institute. Chas. R. Cross 



Boston, Mass., June 19 



The Freshv/ater Medusa 

 In Nature, voh xxii. p. 21S, Prof. AUman by mistake attri- 

 butes to me the conclusion that Limnocodium has no marginal 

 canal, and that its radial canals are not pervious. A reference 

 to Natitre, vol. xxii. p. 147, will show that in my first 

 publication on the subject I gave as a character of the 

 new genus " Radiating canals 4, opening into them,irginal canal. 

 Marginal or ring canal voluminous." I made the same statement 

 in my communication to the Royal Society on June 17, and have 

 not >ince deviated from it. E. Ray Lankester 



Artificial Diamonds 



The process of building up tubes, which Mr. Mallet has been 

 so kind as to suggest to me through your valuable journal, has 

 been tried, but was unsuccessful through the same defect as 

 caused the failure of many of my other experiments, namely, 

 leakage without bursting. Some of the tubes found empty would 

 bear, when cold, a pressure of ten tons on the square inch with- 

 out leaking, showing that the gases escaped through the porosity 

 of the iron at a high temperature. Hydrogen and hydrocarbons 

 seem to go through iron at a red-heat very easily, and the direc- 

 tion in which I am working is to obtain an impervious coating, 

 or a method of "clogging" the iron, as seems to have" some- 

 times taken place in the carbon experiments. 



Experiments conducted since the reading of my paper have 

 convinced me that the ciystallisation of silica and alumina may 

 yet be carried out with ease and certainty, and when I have ren- 

 dered one of these processes a commercial success the experience 

 gained in daily manufacturing operations will enable me to 

 attack the carbon problem with much more certainty of obtaining 

 definite results. 



As I shall be writing an account of tlris work in the autumn 

 I shall feel greatly indebted to any of your readers who, if they 

 come across any not widely known experiments in this direction, 

 will kindly communicate with me, so that I may have all the 

 work don; in this direction before me. Suggestions such as Mr. 

 Mallet's c e valuable to any worker, as the reactions of one brain 

 must always be somewhat similar unless outside stimuli give 

 new directions to its activity. I am always therefore thankful for 

 either suggestion or corrections. J. B. Hannay 



Private Laboratory, Glasgow 



Temperature of the Breath 



The average temperature of the interior of the human body, 

 according to our best authorities, is 9S°"6 F. What is the tem- 

 perature of the breath ? It might naturally be supposed that its 

 temperalure was the same as that of the interior of tlie body, or 

 lower, if it is derived from the lungs, into which it is drawn 

 from the cold outer air. But is this so ? 



The temperature of my body, as shown by the thermometer 

 in the axilla and mouth, is normal, i.e.., about 985°. On rising 

 in the morning, before dressing or eating, I take the thermometer, 

 wrap it up tightly in several folds of a silk handkerchief, and 

 breathe upon it (expiring through the silk immediately over the 

 bulb of the thermometer and inspiring by the nostrils). After 

 five minutes of this operation I examine the thermometer, and 

 find that it indicates a temperature of lo6°'2. At 7 p.m., after 

 brisk walkmg exercise, having eaten nothing since breakfast 

 except a spoonful of boiled rice at I p.m., and having drunk 

 nothing but half a tumbler of water and a mouthful of ginger- 

 beer, I take the temperature of my breath in the manner 

 described, for five minutes. I find the thermometer indicates 

 107°. Again, immediately after dinner, at which only water was 

 drunk, the thermometer shows my breath to have a temperature 

 of loS". At other times the themiometer will not rise under 

 apparently the same conditions higher than 102" to 105". A 

 temperature of 109° was observed by the correspondent of an 

 American journal, but he does not mention under what circum- 

 stances this occurred. 



How is this high temperature produced ? It cannot, as a 

 friend suggested to me, be caused by the condensation of the 

 moisture in the breath by the silk handkerchief, for if the 

 temperature of the breath as it issues from the lungs be the 

 same as that of the lungs themselves, i.e., not exceeding 99°, 

 the silk, soon becoming much hotter, would rather tend to vola- 

 tilise than to condense the moisture of the breath. Is it caused 

 by the friction of the breath upon the fibres of the handkerchief? 

 I know of no observations to show that a high temperatiure would 

 be so caused. Is it the actual temperature of the breath as it 

 issues fi'om the lungs ? If so, then it is by the breath that the 

 system gets rid of its superfluous caloric. For this elevated 

 temperatm-e is not communicated to the blood oxygenated in the 

 lungs ; the blood in the left ventricle of the heart (which receives 

 this oxygenated blood) being, according to some physiologists, 

 lower in temperature than the blood in the right ventricle, which 

 has not yet entered the lungs. 



The few experiments I have made seem to show that the 

 temperature obtained as above described is higher when the 

 surrounding air is warm than when it is cold. This looks as if 

 more caloric passed off by the breath when less can escape from 

 the general surface of the body. 



How these high temperatures are produced in the lungs, if 

 they are developed there, is a mystery. Perhaps some of your 

 readers may be able to explain. 



53, Montagu Square, May 27 R. E. Dudgeon 



Reversals by Memory 



I SHOULD much like to know if it be a common thing for 

 people to reverse the positions of objects in the memory. An 

 artist, on returning from the National Gallery, painted the 

 Timiraire from memory. Taking his picture to compare it with 

 Turner's, he found to his surprise that he had reversed the 

 positions of the ship, tug, sun, &c. His daughter tells me that 

 if she wants to refer to a passage in a book she as often looks 

 for it on a left-hand page, while it is on a right-hand page, o^vice 

 versd. Another lady, on looking at a wood-engraving made from 

 a sketch which she had seen some time previously, asked if the 

 engraver had not reversed everything? These are the only cases 

 known to me. 



Is the following universally true? — 



Let some one write with a blunt instrument the letter P on 

 your forehe.-id, or anywhere on the front half of the head from ear 

 to ear, and the P must be written backwards for _)W( to "see" it 

 correctly. But if it be written anywhere at the back of the 

 head, it must be written correctly both for you and the writer to 

 read it. The change takes place abruptly in a line over each 

 ear. George IIenslow 



Toughened Glass 

 The night before last a lady of my family emptied a paper 

 powder composed of 74 grains of carbonate of potash^ and 74 

 grains of carbonate of soda into a tumbler of what is called 

 toughened glass less than half full of cold water. After stu-ring 

 the mixture she drank the contents, leaving a silver tea-spoon in 

 the tumbler, and then placed the empty tumbler on the table by 

 her side within perhaps a foot of a burning duplex lamp. Ab&ut 

 five minutes afterwards a sharp explosion occurred, which startled 



