I. On Crookes’s force

1877 ◽  
Vol 25 (171-178) ◽  
pp. 553-559 ◽  
Keyword(s):  
Experimental Investigation ◽  
The Other ◽  
Silk Fibre ◽  
Present Communication ◽  
Philosophical Magazine ◽  
Glass Disk ◽  
The Subject ◽  
Dynamical Properties ◽  
Gas Burner ◽  
Glass Envelope

In two papers by one of the authors of the present communication, which appeared in the Philosophical Magazine for March and April 1876, it has been shown that the motion of the blackened disks of a Crookes's radiometer can be explained by the known dynamical properties of the trace of gas which is present, and the term “ Crookes s force is pioposed to designate the reaction which comes into play between the blackened disks and the walls of the exhausted chamber when a difference of temperature exists between them. Shortly after the first of these papers appeared we commenced an experimental investigation of the subject with the view of learning, if possible, the laws to which the force conforms. The investigation is still in progress, and, being ex­ceedingly tedious, it will require a great expenditure of time before it is completed; we propose, however, in this preliminary paper to describe the apparatus and methods of observation employed, and to give some of the results already obtained. If the pressure which is exerted on the blackened pith surfaces reacts on the sides of the glass envelope, it follows that a transparent disk delicately suspended close to a stationary disk of blackened pith ought to move away from the pith, and therefore towards the light, when the pith is illuminated. This inference was submitted to the test of ex­periment by means of an apparatus represented in fig. 1 and constructed as follows :—A piece of elder-pith 2·5 centims. in length and 1·2 centim. in breadth, blackened on one side, was fastened by one end to the interior surface of the bulb of an ordinary boiling-flask (of about 200 cub. centims. capacity) in such a manner that the free end of the pith extended towards the middle of the bulb. A light glass rod with a small magnet on one end, and a disk of thin microscope-glass on the other end, was so suspended in the bulb that the glass disk could be readily balanced in a position nearly parallel with the surface of the blackened pith, and a few millims. distant from it. The silk fibre from which the glass rod was sus­pended hung from a fixed arm at the upper end of a tube, the lower end of which was hermetically fastened into the neck of the flask. An elongation of this tube (not shown in the figure) with a contraction for sealing, served to connect the apparatus with the exhaust-tube of a Sprengel pump. The pump was set in action, and occasionally the flame of an ordinary gas-burner was held at a distance of about 10 centims. from the blackened pith, while the microscope-glass was closely watched. When the gauge of the pump showed a tension of 7 millims., as com­pared with the mercurial column of a barometer standing in the same vessel of mercury, the glass disk was distinctly repelled from the pith and towards the source of light. As the exhaustion was continued the repulsion between the pith and the glass increased. The apparatus was sealed off from the pump when the mercury falling in the exhaust tube had for some days produced a metallic sound. Feeble illumination now caused the glass disk to be forcibly driven away from the pith.

scholarly journals V.—Note on an Undescribed Area of Lower Greensand or Vectian in Dorset

1891 ◽  
Vol 8 (10) ◽  
pp. 456-458 ◽  
Author(s):  
A. J. Jukes-Browne
Keyword(s):  
Lower Cretaceous ◽  
Small Area ◽  
Upper Cretaceous ◽  
The Other ◽  
Present Communication ◽  
The Subject ◽  
Geological Magazine

Until recently no outcrop of the Vectian or Lower Greensand was known to occur between Lulworth on the coast of Dorset and the neighbourhood of Devizes in Wiltshire. It was supposed that, with the exception of a small area of Wealden in the Vale of Wardour, the whole of the Lower Cretaceous Series in Dorset and South Wilts was concealed and buried beneath the overlapping Upper Cretaceous strata. A recent examination of this district however has revealed two areas where the Vectian sands emerge from beneath the Gault. One of these has already been indicated in the pages of the Geological Magazine; the other is the subject of the present communication.

scholarly journals IV.—On a New Species or Discites (Discites Hibernicus) from the Lower Carboniferous Limestone of Ireland

1893 ◽  
Vol 10 (6) ◽  
pp. 251-254
Author(s):  
Arthur H. Foord ◽  
G. C. Crick
Keyword(s):  
New Species ◽  
The Other ◽  
Present Communication ◽  
Lower Carboniferous ◽  
The Subject ◽  
Carboniferous Limestone ◽  
A New Species

The specimen which forms the subject of the present communication was obtained by one of the writers from the Carboniferous Limestone, near Dublin. Although one side of the specimen is covered by matrix, yet the other side and the periphery are so splendidly preserved, and the shell has not been distorted during fossilisation, that the characters of the fossil can be accurately determined (see Woodcut, p. 254).

V. On the heat disengaged during metallic substitutions

1848 ◽  
Vol 138 ◽  
pp. 91-103
Keyword(s):  
Thermal Effects ◽  
The State ◽  
The Other ◽  
Dilute Solution ◽  
Present Communication ◽  
Philosophical Magazine ◽  
Negative Element ◽  
General Law ◽  
Metallic Element ◽  
Quantity Of Heat

In the present communication I propose to give an account of some new investiga­tions on the heat disengaged in chemical actions, which may be considered a continuation of my former inquiries on the same subject. The greater number of the experiments to be detailed in this paper were made some years ago, and the con­clusion at which I arrived was briefly announced in the Philosophical Magazine for August 1844. More recently, I have taken an opportunity to repeat many of my former experiments and to add new ones on the same subject, all of which confirm the general results formerly obtained. Having originally observed that although a very limited number of bases (potash, soda, barytes and strontia) develope nearly the same quantity of heat, when a chemical equivalent of each enters into combination with an acid, yet that the greater number of bases differ most widely from one another, when so treated, while on the other hand, that different acids (taken in the state of dilute solution) produce with the same base nearly the same amount of heat, I ventured to draw the general inference that the thermal effects produced are more intimately connected with the basic, or electro-positive, than with the acid, or electro-negative element. In conformity with this view, it appeared probable that in the decomposition of solutions of neutral salts by the addition of bases or metallic bodies, the nature of the acid or electro-negative element of the compound would exercise no special influence on the result. I have already endeavoured to establish by experiment the truth of this principle in the case of basic substitutions, and, in the present memoir, I propose to extend the same general law to the other case, in which one metallic element re­places, or is substituted for another.

scholarly journals XX. Researches in physical geology

1839 ◽  
Vol 129 ◽  
pp. 381-423 ◽  
Keyword(s):  
The Other ◽  
Free Motion ◽  
Present Communication ◽  
Rate Of Increase ◽  
Mathematical Investigation ◽  
The Subject ◽  
Physical Geology ◽  
Limiting Case

Before I proceed to the discussion of the question which forms the principal sub­ject of the present communication, I shall offer some general remarks on the refri­geration of the globe, as introductory not only to this memoir, but to others which I hope hereafter to bring under the notice of the Society. In the first place, we may observe that there are two distinct processes of cooling, of which one belongs to bodies which are either solid or imperfectly fluid, and is termed cooling by conduction , and the other to masses in that state of more perfect fluidity which admits of a free motion of the component particles among themselves. In this case the cooling is said to take place by circulation or convection . The na­ture of the former process has been ascertained with considerable accuracy by ex­periment, and the laws of the phenomena have been made the subject of mathematical investigation, but of the exact laws of cooling by the latter process we are compara­tively ignorant. It is manifest, however, that since time must be necessary for the transmission of the hotter and lighter particles from the central to the superficial parts of the mass, as well as for that of the colder and heavier particles in the oppo­site direction, the temperature must increase with the depth beneath the surface; and, moreover, that this increase will be the more rapid, the more nearly the fluidity of the mass approaches that limit at which this process of cooling would cease, and that by conduction begin, since the rapidity of circulation would constantly diminish as the fluidity should approximate to that limit. But still, even in this limiting case, it seems probable that the tendency to produce an equality of temperature throughout the mass will be much greater, and consequently the rate of increase of temperature in approaching the centre much less, than if the cooling of the mass had proceeded by conduction during the same time, the conductive power being very small.

scholarly journals On a pair of ciliated grooves in the brain of the ammocœte apparently serving to promote the circulation of the fluid in the brain-cavity

1902 ◽  
Vol 69 (451-458) ◽  
pp. 485-494 ◽  
Keyword(s):  
New Zealand ◽  
The Other ◽  
Present Communication ◽  
Late Professor ◽  
Geotria Australis ◽  
The Subject ◽  
The Brain ◽  
Interesting Species

The peculiar and apparently hitherto undescribed structures which form the subject of the present communication, were first discovered in the course of an as yet unfinished investigation of the parietal organs in the New Zealand Lamprey ( Geotria australis ). The Ammocœte of this interesting species is known to us only through two specimens: one of these was briefly described by Kner in 1869; the other was for many years in the Museum of the Otago University, Dunedin, and was forwarded to me for investigation by the present curator, Professor W. B. Benham, D. Sc., to whom I desire to express my indebtedness for his great kindness. The specimen which I have thus had the opportunity of investigating was labelled in the handwriting of the late Professor T. J. Parker, F. R. S.—“Ammocœtes stage of Geotria—Opoho Creek.

scholarly journals XXI. Experimental researches on atomic weights

1833 ◽  
Vol 123 ◽  
pp. 523-544 ◽  
Keyword(s):  
First Principles ◽  
Atomic Weight ◽  
Point Of View ◽  
Relative Accuracy ◽  
The Other ◽  
Present Communication ◽  
Present Essay ◽  
The Subject ◽  
Important Object ◽  
Experimental Researches

The present communication may be viewed as the continuation of an Essay on the Composition of the Chloride of Barium, which was honoured with a place in the Philosophical Transactions for the year 1829. In resuming the subject after such a long interval, I feel it right to apologize to the Society for the unfinished state in which that Essay has hitherto been left,—an omission far from voluntary, and entirely due to circumstances not subject to my own controul. In one point of view, however, the delay has been advantageous: it has afforded an opportunity to chemists to verify or correct the results contained in my first Essay, and has enabled me to repeat and extend my researches. The object which I proposed to myself in commencing the present inquiry, was to re-examine some of those estimates which chemists have occasion to use continually as elements in their calculations, and to confide in as the foundation of their doctrines. With this view I undertook to determine the relative accuracy of the atomic weights which the British and Continental chemists respectively employ; and several circumstances induced me to begin by analysing the chloride of barium. Dr. Thomson, on whose experiments the British chemists relied, had obtained so many of his results by means of the chloride of barium, that any material error in the constitution of that compound would necessarily vitiate a large part of his table of equivalents; and if, on the other hand, the estimate of Dr. Thomson proved to be correct, an important error would be chargeable against Berzelius, whose numbers are very generally adopted on the Continent. The result of the inquiry is now well known: the source of fallacy, pointed out in my first communication, has been admitted by Dr. Thomson in the new edition of his System of Chemistry, and he has accordingly changed the equivalent of barium from 70 to 68. The inevitable consequence of this change must be apparent to every one who is acquainted with the method of analysis so frequently resorted to by Dr. Thomson. Many of the experiments described in his First Principles of Chemistry are now at irreconcilable variance with each other, and, if relied upon at all, subvert the conclusions which they once appeared to establish. Nor can those parts of his work which are not subject to this criticism be safely applied to the purposes of science. His view, for instance, of the composition of the compounds of oxygen with phosphorus, arsenic, and antimony, has been lately abandoned by himself; and in the course of the present Essay I shall have occasion to prove, that the atomic weights which he has employed for silver and chlorine are likewise inadmissible. His analysis of sulphate of zinc, which was made, to use Dr. Thomson’s own words, “the foundation on which he endeavoured to rear the whole subsequent doctrine of the atomic weight of bodies,” is peculiarly objectionable. Besides being vitiated by his error in the equivalent of barium, the oxide of zinc was determined by a method which involved an error in principle, and was in practice so complex as to be unfit for the extremely important object which it was intended to serve.

Rubber, Polyisoprenes and Allied Compounds. II. The Molecule-Linking Capacity of Free Radicals and Its Bearing on the Mechanism of Vulcanization and Photo-Gelling Reactions

1943 ◽  
Vol 16 (3) ◽  
pp. 467-478
Author(s):  
Ernest Harold Farmer ◽  
Stephen E. Michael
Keyword(s):  
Experimental Investigation ◽  
Free Radicals ◽  
Benzoic Acid ◽  
Organic Acids ◽  
Benzoyl Peroxide ◽  
Chemical Nature ◽  
The Other ◽  
Benzenoid Hydrocarbons ◽  
The Subject ◽  
The One

Abstract Ostromislensky discovered that benzoyl peroxide when heated with rubber to 140° brought about a species of vulcanization of the rubber, the chemical nature of which has been the subject of much conjecture and experimental investigation. It was thought at first that the process was essentially one of oxidation and, indeed, free benzoic acid derived from the peroxide was isolated by Ostromislensky from the reaction product; but van Rossem, Dekker, and Prawirodipoero found that, although much benzoic acid was liberated during the reaction, some became united with the rubber, and could afterwards be freed by saponification. Van Rossem and his collaborators, however, were unable to correlate the accumulated observations with the previously published generalizations of Gelissen and Hermans concerning the nature of the reactions between benzoyl peroxide on the one hand and numerous substances, including alcohols, organic acids, and saturated and benzenoid hydrocarbons, on the other; nevertheless, they agreed with Gelissen and Hermans on one point, viz., that to some extent cleavage of the peroxide with formation of benzoic acid probably occurred, and they suggested that the concomitant reaction was a dehydrogenation of the rubber, the latter possibly becoming cross-linked as a result (2C5H8+PhCO·O·O·COPh→—C5H7·C5·H7—+2PhCO2H). Subsequently, Ostromislensky, following useful observations by Bock, made a new examination of the reaction, and concluded that it proceeded according to the equation:

scholarly journals IV. On the elasticity and viscosity of metals

1865 ◽  
Vol 14 ◽  
pp. 289-297 ◽  
Keyword(s):  
Experimental Investigation ◽  
Natural Philosophy ◽  
Present Communication ◽  
Physical Laboratory ◽  
The Subject ◽  
Metallic Wires ◽  
The University ◽  
Moduli Of Elasticity ◽  
The Way

Among the experimental exercises performed by students in the physical laboratory of the University of Glasgow, observations on the elasticity of metals have been continued during many years. Numerous questions of great interest, requiring more thorough and accurate investigation, have been suggested by these observations; and recently they have brought to light some very unexpected properties of metallic wires. The results stated in the present communication are, however, with one or two exceptions, due to the careful experimenting of Mr. Donald Macfarlane, official assistant to the Professor of Natural Philosophy, whose interested and skilful cooperation have been most valuable in almost everything I have been able to attempt in the way of experimental investigation. The subject has naturally fallen into two divisions, Viscosity, and Moduli of Elasticity.

Golgi Apparatus and Melanogenesis: Ultrastructural Study of a Human Cellular Blue Nevus (Melanocytoma)

1973 ◽  
Vol 31 ◽  
pp. 380-381
Author(s):  
S.R. Allegra
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Ultrastructural Study ◽  
The Other ◽  
Blue Nevus ◽  
Normal Complement ◽  
Golgi Vesicles ◽  
Golgi System ◽  
The Subject ◽  
Cellular Blue Nevus

The respective roles of the ribo somes, endoplasmic reticulum, Golgi apparatus and perhaps nucleus in the synthesis and maturation of melanosomes is still the subject of some controversy. While the early melanosomes (premelanosomes) have been frequently demonstrated to originate as Golgi vesicles, it is undeniable that these structures can be formed in cells in which Golgi system is not found. This report was prompted by the findings in an essentially amelanotic human cellular blue nevus (melanocytoma) of two distinct lines of melanocytes one of which was devoid of any trace of Golgi apparatus while the other had normal complement of this organelle.

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